WO2014200301A1 - Electronic device with code module and method for processing code using same - Google Patents

Abstract

An electronic device according to the present invention includes: a temporary password key manager for receiving a message encrypted with a temporary password key limited in the number of uses and determining whether the temporary password key is effective depending on whether a proof value corresponding to the temporary password key exists in a temporary password key table; and a code module including a decryption unit for not decrypting the encrypted message if the temporary password key is not effective.

Description

Electronic device having cryptographic module and its cryptographic methods

The present invention relates to an electronic device having a cryptographic module and its cryptographic methods.

As hacking techniques evolve, the cost of response increases. In particular, with the advent of new hardware-based implementation environments and technologies such as RFID, smart cards, smartphones, sensors, ubiquitous, and the Internet of Things, cryptographic communication techniques that provide low power, low cost, high efficiency, and high security that can be used in their communication environments. The demand for is increasing.

One of the most obstacles in terms of countermeasures against hacking is side channel attack. In particular, since subchannel attacks using electromagnetic waves and sound are not only difficult to detect but also easily obtainable attack information, security measures should be established. However, due to the excessive increase in the implementation cost, it is difficult to implement the actual response method.

Template attack among side channel attacks is a powerful attack method that can be applied when the same encryption operation can be repeatedly performed. Thus, control over cryptographic operations is required so as not to repeat the same cryptographic operations.

 At the same time, you must also consider the safety against Denial of Service (DoS) attacks. In the case of DoS attacks, resources are wasted, which not only shortens the life of battery-based devices, but also prevents legitimate cryptographic operations. Therefore, it is important to quickly detect and block the attacker's indications of wasting resources such as DoS attacks.

The present invention proposes a cryptographic operation method that provides strong security against side channel attacks including DoS attacks and template attacks.

According to an embodiment of the present disclosure, a method of decrypting an electronic device having an encryption module includes: receiving a message encrypted by a temporary secret key; On the basis of whether an entry consisting of the temporary secret key and a value (eg, hash or encryption, or the temporary secret key itself) for verifying the temporary secret key exists in the temporary secret key table of the cryptographic module. Determining whether the temporary secret key is valid; And if the temporary secret key is invalid, not decrypting the encrypted message.

In an embodiment, if the temporary secret key is valid, the method further includes decrypting the encrypted message.

In an embodiment, determining whether the temporary private key is valid comprises determining that the temporary private key is invalid if the entry was used in a previous decryption operation.

In an embodiment, the determining whether the temporary private key is valid may include determining that the temporary private key is not valid if the number of times the entry has been used in a previous decryption operation is greater than or equal to a predetermined value. .

The temporary secret key table may include a plurality of entries including an index, a temporary secret key, and a verification value of the temporary secret key (for example, a verification value may be the temporary secret key itself). Include.

The method may further include deleting an entry for which a temporary secret key is not valid among the plurality of entries from the temporary secret table; And adding a new entry to the temporary secret table, the new entry consisting of a new index, a new temporary secret key corresponding to the new index, and a value for verifying the new temporary secret key.

The method may further include determining, from the temporary secret table, whether the number of entries in which the temporary secret key is invalid among the plurality of entries is greater than or equal to a predetermined value; and wherein the number of the invalid entries is determined in advance. Updating the temporary secret table when greater than or equal to the value.

In an embodiment, the method may further include receiving an authentication code generated by the temporary secret key and the message.

The method may further include stopping the verification operation on the authentication code when the temporary secret key is invalid; And when the temporary secret key is valid, performing a verification operation on the authentication code.

The method may further include not decrypting the encrypted message when a verification operation for the authentication code fails.

The method may further include decrypting the encrypted message when the verification operation on the authentication code is successful.

An electronic device according to an embodiment of the present disclosure receives a message encrypted with a temporary secret key having a limit on the number of times of use, and based on whether a verification value corresponding to the temporary secret key exists in the temporary secret key table. A temporary secret key manager for determining whether the secret key is valid; And a decryption unit that does not decrypt the encrypted message if the temporary secret key is invalid.

In an embodiment, the temporary secret key manager generates another temporary secret key.

In an embodiment, the cryptographic module includes an encryption unit for encrypting the message with another temporary secret key.

In an embodiment, the cryptographic module uses a message authentication code and a cryptographic primitive function.

In an embodiment, the message authentication code is generated to authenticate a message and additional head information of the message.

An encryption method of an electronic device having an encryption module according to an embodiment of the present disclosure may include generating a plurality of entries including a temporary secret key having a limit on the number of times of use and a verification value of the temporary secret key; Selecting any one of the plurality of entries; Encrypting the message using the temporary private key of the selected entry; And generating an authentication code using the used temporary secret key and the message.

In an embodiment, the temporary secret key is generated on a sequential basis.

In an embodiment, the temporary secret key is protected using an encryption operation, a hash function, or a synchronization operation.

In an embodiment, the method may further include transmitting the verification value and the encrypted message to another cryptographic module.

As described above, the electronic device having the cryptographic module and the encryption / decryption methods thereof according to the present invention can fundamentally block the subchannel attack by stopping the decryption operation according to the number of times the temporary secret key is used.

1 is a diagram illustrating an encryption system for explaining the concept of the present invention by way of example.

2 is a flowchart illustrating an encryption method of an electronic device having an encryption module according to an embodiment of the present disclosure.

3 is a diagram illustrating a secret secret key generation method by a sequential processing method.

4 is a diagram illustrating an embodiment of a method of encrypting a temporary secret key.

5 is a diagram illustrating an embodiment of a method of hashing a temporary secret key.

6 illustrates a modified ECB mode according to an embodiment of the present invention.

7 illustrates a modified CBC mode according to an embodiment of the present invention.

8 illustrates a modified CTR mode according to an embodiment of the present invention.

9 is a flowchart illustrating a decryption method of an electronic device having an encryption module according to an embodiment of the present disclosure.

10 is a flowchart exemplarily illustrating an encryption code-based encryption method (simple password authentication method) according to an embodiment of the present invention.

11 is a diagram for describing a block cipher-based cipher authentication and decryption verification method according to an exemplary embodiment of the present invention.

12 is a diagram illustrating a method of generating a mask train from a temporary secret nonce.

FIG. 13 is a diagram illustrating an example of a change to the checksum generation method illustrated in FIG. 11.

FIG. 14 is a diagram illustrating an example of changing a last message block processing method and a checksum illustrated in FIG. 11.

FIG. 15 is a diagram illustrating an example of changing a mask value applying method when processing the last message block illustrated in FIG. 14.

FIG. 16 is a diagram illustrating an example of a change to a case where the additional information shown in FIG. 14 is to be authenticated together.

17 is a diagram illustrating an example of a method of updating a key of every block cipher without applying a mask value according to an embodiment of the present invention.

FIG. 18 is a diagram illustrating an example of a change to a case where the additional information shown in FIG. 17 is to be authenticated together.

FIG. 19 is a diagram illustrating an example of updating a key by using a temporary secret value when processing the last checksum illustrated in FIG. 17.

20 is a diagram illustrating an example of defining a mask value using a key value of a block cipher according to an embodiment of the present invention.

21 is a flowchart illustrating a decryption verification method of an electronic device having an encryption module according to an embodiment of the present disclosure.

FIG. 22 is a diagram illustrating an example of generating temporary secret nonce (Ni, Ni ') by a sequential processing method using a substitution function P according to an embodiment of the present invention.

FIG. 23 is a diagram illustrating an example of designing an encryption authentication scheme based on prefix free message padding based on a substitution function according to an embodiment of the present invention.

FIG. 24 is a diagram illustrating an example of designing an encryption authentication scheme based on arbitrary reversible message padding based on a substitution function according to an embodiment of the present invention.

FIG. 25 is a diagram illustrating an example of designing an encryption authentication scheme based on arbitrary reversible message padding using a substitution function and a non-zero constant value according to an embodiment of the present invention.

FIG. 26 is a diagram illustrating an example of a method of processing additional information illustrated in FIG. 23 and changing an authentication code value having an arbitrary length to be generated.

27 is a diagram illustrating an example of generating temporary secret nonce (Ni, Ni ', Ni' ') by a sequential processing method using a compression function f according to an embodiment of the present invention.

FIG. 28 is a diagram illustrating an example of designing an encryption authentication scheme based on prefix free message padding based on a compression function f according to an embodiment of the present invention.

FIG. 29 is a diagram illustrating an example of designing an encryption authentication scheme based on arbitrary reversible message padding based on a compression function f according to an embodiment of the present invention.

30 is a diagram illustrating an example of designing an encryption authentication scheme based on arbitrary reversible message padding using a compression function and a non-zero constant value.

31 is a view showing a modified CBC mode according to an embodiment of the present invention.

32 is a view showing a modified CBC mode according to an embodiment of the present invention.

33 shows OMAC.

34 is a diagram showing PMAC.

35 is a diagram exemplarily illustrating an encryption / decryption operation using a temporary secret key table (TPK Table) according to an embodiment of the present invention.

36 is a diagram illustrating a temporary secret key table according to an embodiment of the present invention.

37 is a diagram exemplarily illustrating a method for adding an entry of a temporary secret key table according to an embodiment of the present invention.

38 is a diagram illustrating a temporary secret key table update method according to an embodiment of the present invention.

1 is a view showing the best mode for practicing the present invention.

DETAILED DESCRIPTION Hereinafter, the contents of the present invention will be described clearly and in detail so that those skilled in the art can easily implement the drawings.

Template attack among side channel attacks is a powerful attack method that can be applied when the same encryption operation can be repeatedly performed. Thus, control over cryptographic operations is required so as not to repeat the same cryptographic operations.

 At the same time, you must also consider the safety against Denial of Service (DoS) attacks. In the case of DoS attacks, resources are wasted, which not only shortens the life of battery-based devices, but also prevents legitimate cryptographic operations. Therefore, it is important to quickly detect and block the attacker's indications of wasting resources such as DoS attacks.

The present invention proposes a cryptographic operation method that provides strong security against side channel attacks including DoS attacks and template attacks.

1 exemplarily shows a cryptographic system 10 for explaining the concept of the present invention. Referring to FIG. 1, the cryptographic system 10 includes a first electronic device 100 and a second electronic device 200 that perform cryptographic communication through an external channel 11. Here, the external channel 11 may be a channel protected from an attacker's attack.

Each of the first electronic device 100 and the second electronic device 200 may include cryptographic modules 120 and 220 for performing cryptographic communication and cryptographic operation. In FIG. 1, for convenience of description, the first electronic device 100 transmits encrypted data generated by performing an encryption operation, and the second electronic device 200 transmits the encrypted data received from the first electronic device 100. Suppose you perform a cryptographic operation using The cryptographic operation includes various cryptographic operations such as encryption and decryption, authentication, digital signature, and key sharing.

The cryptographic module 120 of the first electronic device 100 includes a first temporary secret key manager 122 and an encryption unit 224.

The first temporary private key manager 122 generates a temporary private key ("TPK") required for the encryption operation. Here, the temporary secret key (TPK) has a limit on the number of uses. That is, the temporary secret key (TPK) can be used one or more times, but not more than that. For example, the temporary secret key (TPK) may be a temporary secret value (or key), such as a one-time password, secret nonce, session key.

The encryption unit 224 performs a cryptographic operation using the temporary secret key TPK. The data values C generated through the encryption operation are transmitted to the external channel 11 through the internal channel 101 of the first electronic device 100. At this time, it is possible to transmit a value C0 that is difficult to infer corresponding to the temporary secret key TPK. Here, the transmitted verification value C0 is a verification value for the temporary secret key TPK. In an embodiment, the verification value C0 may be a hash value of the temporary secret key TPK. In another embodiment, the verification value C0 may be an authentication code value of the temporary secret key TPK. In another embodiment, the verification value C0 may be an encrypted value of the temporary secret key TPK. The verification value C0 may be the same as or different from the verification value in the temporary secret value table in the cryptographic module. In the case of generating the C0 value by encryption, which will be described later, the verification value which is the subject of verification in the temporary secret value table may be the temporary secret value, and C0 may be the cipher text of the temporary secret value. Alternatively, if the temporary secret key is synchronized between the two cryptographic modules, C0 can be an empty string.

Although not shown, there may be an appropriate interface between the inner channel 101 and the outer channel 11 for changing to data transmittable to the outer channel 11.

The cryptographic module 200 of the second electronic device 200 includes a second temporary secret key manager 222 and a decryption unit 224. In this case, the decryption unit 224 may include a process of performing decryption or verifying authentication.

The second temporary secret key manager 222 determines from C0 whether a corresponding temporary secret key (TPK) is in its internal memory, verifies / determines whether it is a valid temporary secret key (TPalid), and decrypts it accordingly. Unit 224 may be activated. For example, if the temporary secret key TPK is a valid temporary TPK, an activation signal EN may be generated. The decryption unit 224 performs a process on the encrypted data received from the first electronic device 100 in response to the activation signal EN. According to an embodiment of the present disclosure, each of the cryptographic modules 120 and 220 may be implemented so as not to trust the first electronic device 100 and the second electronic device 200, which are driving subjects. In an embodiment, the cryptographic modules 120 and 220 may share a secret key with each other in advance to generate temporary secret values.

In an embodiment, the valid temporary TPK may be a temporary secret key that is not used in a previous cryptographic operation.

In another embodiment, the valid temporary TPK may be a temporary private key used up to a predetermined number of times in a previous cryptographic operation. The second temporary secret key manager 222 may verify / determine whether it is a valid temporary secret key (TPalid TPK) based on whether the temporary secret key (TPK) is used or how many times it is used.

The decryption unit 224 of the present invention does not initiate a decryption operation unless the temporary secret key TPK is not a valid temporary secret key TPK. That is, if the temporary secret key TPK is not a valid temporary TPK, the operation of the cryptographic module 220 may be immediately stopped.

Meanwhile, in FIG. 1, the encryption module 120 of the first electronic device 100 is illustrated in terms of encryption, and the encryption module 220 of the second electronic device 200 is only illustrated in terms of decryption. Here, the cryptographic modules can perform various cryptographic operations, such as encryption and decryption and authentication, digital signature generation and verification. The cryptographic module 120 of the first electronic device 100 may include components 222 and 224 of the cryptographic module 220 of the second electronic device 200, or may include the cryptographic module of the second electronic device 200. 220 may include components 122 and 124 of the cryptographic module 12 of the first electronic device.

The cryptographic system 10 according to an embodiment of the present invention performs a cryptographic operation in consideration of whether the temporary secret key (TPK) is used in the previous cryptographic operation or the number of repetitive use, thereby subchannel and DoS attacks including template attacks. Secure cryptographic communication can be performed.

In the following, we will explain in detail how to generate and use a temporary secret key (TPK) and how to perform cryptographic operations using the temporary secret key (TPK).

2 is a flowchart illustrating an encryption method according to an embodiment of the present invention. 1 and 2, the encryption method is as follows. A temporary secret key TPK that is not used in the temporary secret key manager 122 or used less than a predetermined number of times is generated (S110). The temporary secret key (TPK) generated so as not to be known from the attacker is protected (S120). For example, the hash value C0 of the temporary secret key TPK may be generated to protect the temporary secret key TPK. Subsequently, the message is encrypted using the temporary secret key TPK in the encryption unit 224 (S130). Finally, it sends an encrypted message to the other party with C0.

In the following, the encryption method will be described in detail.

Temporary Secret Key (TPK) Generation (Figure 2, step S110)

A temporary secret key (TPK) is important secret information that will be used, such as a session key or a one-time password for performing cryptographic operations. As a method of generating a temporary secret key (TPK), a generation method based on sequential processing and a method of dealing with the same are described.

3 is a diagram illustrating a secret secret key generation method by a sequential processing method. Referring to FIG. 3, a temporary secret key (TPK) or a nonce (N) value using a shared key K and a block cipher E shared between two cryptographic modules 120, 220 (see FIG. 1). Are generated sequentially. If the first nonce (1, N1) is used for the first encryption operation, the second nonce (2, N2) is used for the next second encryption operation, and the third nonce (3, N3) for the third encryption operation. Will be used. Alternatively, temporary secret nonce values may be used in various ways. A characteristic of the sequential processing scheme shown in FIG. 3 is that the block cipher operation is performed only once to generate a nonce to be used as a new temporary secret key (TPK) to be used next. This can provide maximum implementation efficiency. Alternatively, if a nonce value can be defined using only a part of the block cipher output value, even if a particular nonce value is exposed to an attacker, the nonce used before or after it can be protected. Alternatively, a new temporary secret key (TPK) can be generated several times of block cipher operations.

Generated temporary secret key (TPK) protection (Figure 2, step S120)

The generated temporary secret key (TPK) is dangerous if known to the attacker. The temporary secret key TPK can be protected by generating a verification value C0 for the temporary secret key TPK using the following three methods. The first is the encryption method, the second is the hash function, and the third is the temporary secret key (TPK) synchronization.

4 is a diagram exemplarily illustrating temporary secret key (TPK) protection according to an encryption method. K is a secret key value shared between the two cryptographic modules 120, 220, and constant is any fixed constant value. An encryption module (eg, 120 of FIG. 1) wishing to perform encryption generates an encrypted nonce (C0) by encrypting the generated nonce (N), and encrypts the generated nonce (C0) with a relative cipher. To the module (eg, 220). The encrypted nonce is a value that cannot be deduced by an attacker who does not know the shared key (K). In this case, the XOR operation for protecting the nonce N from the encrypted nonce C0 may be efficiently implemented to be secured by the subchannel attack. At this time, in order to decrypt the nonce N from the encrypted nonce C0, the value of the shared key K must be shared in advance between two correct devices which want to communicate.

The temporary secret key manager (e.g., 122) stores the nonce value and its index number in a table. The table can be any memory space in the cryptographic module. For example, if you store (1, N1), (2, N2), and (3, N3) and use N1 and delete it, instead of (1, N1), instead of (1, N1), you fill the table with (4, N4) instead. You can add new nonce values to the table like this. If N1 is not used due to communication problems, N1 may be deleted after a certain time to prevent memory leaks. The temporary secret key manager may add information on the number of times each nonce value is used to each entry in order to repeatedly use the nonce value up to a predetermined number.

5 is a diagram illustrating a temporary secret key (TPK) protection according to the hash function (H) scheme by way of example. In FIG. 5, for convenience of explanation, it is assumed that the hash function H is a one-way hash function. In order to protect the temporary secret value nonce (N), its hash value (C0) is generated. At this time, the hash function H does not include any secret information. Also, without knowing the temporary secret key (TPK), the attacker will not be able to infer the hash value (C0).

Since the nonce N is random, no information about the nonce N from the hash value C0 is exposed from subchannel attacks such as power and electromagnetic waves. Each of the two cryptographic modules 120, 220 stores the index and temporary secret key nonce (N) and their hash values (C0 (= H (N))) as a table in memory in the module. That is, the table includes an entry consisting of a hash value C0 and a nonce value (index, N). Accordingly, the counterpart cryptographic module (eg, 240) may use the table to obtain the corresponding index and temporary secret value nonce (N) from the hash value (C0).

In an embodiment, the temporary secret value nonce N and its hash value C0 used for more than a limited number of times may be deleted from the table so that it is no longer available. That is, the corresponding entry can be deleted from the table.

In an embodiment, a new temporary secret value nonce (N) and its hash value (C0) may be generated and updated in the table. For example, (1, N1, C0_1 = H (N1)), (2, N2, C0_2 = H (N2)), and (3, N3, C0_3 = H (N3)) related tables are safely stored within the module. When limiting the number of times of use of each nonce (N1, N2, N3) to one time, once the nonce (N1) is used, the entry (1, N1, C0_1 = H (N1)) is deleted from the storage space. The new entry (4, N4, C0_4 = H (N4)) may be filled in place. If N1 is not used and N2 is used immediately due to a communication problem or an interruption of an attacker's communication, the memory leak can be blocked since N1 is deleted and filled with another nonce value after a certain time. . The temporary secret key manager may add information on the number of times each nonce value is used to each entry in order to repeatedly use the nonce value up to a predetermined number.

When protecting the temporary secret key (TPK) according to the hash function method, since the internal state values of the hash function-based method are random values, strong security can be provided against non-invasive subchannel attacks such as power consumption, electromagnetic waves, and sound. .

More specifically, it is assumed that two cryptographic modules A and B wishing to communicate share a shared key K, and each cryptographic module has a TPK table of the same size. In this case, the sizes of the TPK tables may be different. For example, a table has 10 entries. The description here is based on hash. The temporary key usage count is 1, for example. In this case, the TPK table may sort the entries by using the C0 value for efficient C0 search.

Step 1. Each of the two cryptographic modules A and B generates 10 entries from the shared key K. At this time, each entry becomes an index, a temporary secret key, and a hash value. That is, the first entry is (1, N1, C0_1 = H (N1)), and the second entry is (2, N2, C0_2 = H (N2)). Thus, the tenth entry (10, N10, C0_10 = H (N10)) occurs. At this time, the table cannot know the remaining values other than the two cryptographic modules A (see FIG. 1 and 120) and B (see FIG. 1 and 220).

Step 2. After defining the table as in Step 1, the two cryptographic modules begin communicating. The cryptographic data (C) obtained by performing a cryptographic operation using N values, which are temporary secret values, is transmitted to the counterpart according to a protocol established between the two devices. Consider the case where A sends to B. In this case, the index is used from the smallest N values. A generates the encrypted data C using the temporary secret value Ni used at any point in time. Then delete (i, Ni, C0_i) from the TPK table and fill it with the new index. In this case, instead of updating the entry every time, it may be a regular period, and the update time may be shortened by sorting the entries using the C0 value.

A sends C0_i value corresponding to Ni to C together with the cipher data C. The index i value is not sent together. The reason is that i is an index value, so that the attacker can easily infer and send (i, C0 ') to the attacker as if it were A, then B verifies that C0_i and C0_i' corresponding to Ni corresponding to i are the same. Or check if the hash value of Ni is equal to C0_i '. If an attacker repeatedly asks about the same i value, there is a risk that the Ni or C0_i value will be exposed by side channel attacks such as template attacks. Therefore, in the present invention, i value is not sent. B then checks if C0_i exists in its TPK table, and if C0_i does not exist, no further cryptographic operations are performed.

If there is a C0_i value in the TPK table, the cryptographic operation is performed using Ni. If there is an entry (j, Nj, C0_j) for all js less than or equal to i in B's TPK table, it is deleted and filled with new entries. In this case, instead of updating the entry every time, it may be a regular period, and the update time may be shortened by sorting the entries using the C0 value.

If B wants to send encrypted data to A, he continues in the same way.

There is also a way to synchronize the temporary secret key. Never send information related to a temporary secret key (TPK) to the other cryptographic module. This requires synchronization of nonce values between the two cryptographic modules 120 and 220.

On the other hand, the temporary secret key validation method of the present invention is not limited to the above-described method, it can be implemented in various ways.

Message encryption using a temporary secret key (TPK) (FIG. 2, step S130)

After the encryption operation is performed using the temporary secret key (TPK), the hash value of the temporary secret key (TPK), which is a verification value corresponding to the temporary secret key, is sent to the counterpart. At this time, the other party determines whether there is a corresponding temporary secret key (TPK) from C0, and if the temporary secret key (TPK) corresponding to C0 exists, determines that it is available and performs a cryptographic operation. The verification value C0 here may be the same as or different from the verification value in the temporary secret key table owned by the temporary secret key manager.

Fixed secret values should not be used repeatedly to perform cryptographic operations to protect against side channel attacks. In other words, the encryption process will be designed to continuously change the internal state value using the temporary secret key (TPK). That is, block keys to be used for an internal block cipher are generated using a temporary secret key to apply different block keys to each block cipher.

6 to 8 are diagrams illustrating an encryption scheme according to an embodiment of the present invention. For convenience of explanation, it is assumed that the temporary secret key N has been hashed. Where H is a hash function and the block cipher key is updated each time using the temporary secret key (N). When encrypting the input message (M), the final output value is C = C0 || C1 || ... An encryption scheme according to an embodiment of the present invention may be implemented such that the secret value N is not repeatedly used. This can be implemented with a temporary secret nonce value (N).

FIG. 6 is a diagram illustrating a modified electronic book (ECB) mode of a block cipher algorithm according to an embodiment of the present invention. Referring to FIG. 6, the plain text is divided into blocks of a certain size, and each block is encrypted with different keys generated from a given temporary secret value.

FIG. 7 illustrates a modified cipher-block chaining (CBC) mode of a block cipher algorithm according to an embodiment of the present invention. Referring to FIG. 7, an XOR operation of the current plaintext block and the immediately preceding cipher block is used as an input of an algorithm, and each block is encrypted with different keys generated from a given temporary secret value.

8 is a modified CTR (counter) mode of the block cipher algorithm according to an embodiment of the present invention. Referring to Figure 8, a block cipher is used like a stream cipher. The constant values (const, const + 1, const + 2, ...) entered into the blocks are counted up sequentially, and each block is encrypted with different keys generated from the given temporary secret value. On the other hand, the encryption method of the present invention is not limited to the block encryption method shown in Figs. Similar to the above, it is applicable to encryption schemes based on various cryptographic primitives, such as block ciphers.

9 is a flowchart illustrating a decoding method according to an embodiment of the present invention. 1 and 9, the decoding process proceeds as follows.

The encrypted message C is input to the second electronic device 200 through the external channel 11 (S210). It is determined whether the temporary secret key TPK used to generate the encrypted message C in the temporary secret key manager 222 is valid (S220). In other words, if the temporary secret key (TPK) has never been used in a previous encryption / decryption operation or the number of times of use does not exceed a predetermined value, the temporary secret key (TPK) is a valid temporary secret key (Valid TPK). If the temporary secret key TPK is valid, the message C encrypted by the decryption unit 224 is decrypted (S330). On the other hand, if the temporary secret key TPK is not valid, the operation of the encryption module 220 including the decryption unit 220 is stopped (S335).

In the decryption method according to an embodiment of the present invention, after verifying the temporary secret key (TPK), the decryption operation may be determined according to the result.

The decoding operation will be described in detail below.

Check whether the temporary secret key (TPK) is used repeatedly (FIG. 9, step S210)

The decryption step is to limit the number of times of use of the same verification value C0. For example, once used hashes or encrypted verification values C0 may no longer be used. Whether repeated use of the hash or the encrypted verification value C0 is important because implementations that are not guaranteed to be random are vulnerable to side channel attacks. Therefore, the temporary secret key (TPK) corresponding to the hash or encrypted verification value (C0) is determined by using a table managed by the temporary secret key manager, and is repeated if it is already used or for a limited number of times. If used, the decryption operation will be aborted.

Decrypt cipher text using temporary secret key (TPK) (FIG. 9, S230, S235)

After verifying that the temporary secret key (TPK) has not been used repeatedly, the temporary secret key (TPK) is calculated. After that, the decryption operation is performed on the input ciphertext C.

Meanwhile, the encryption / decryption operation of the present invention may add an authentication method.

About block cipher-based encryption / decryption + authentication method

10 is a flowchart exemplarily illustrating a block encryption method combining an authentication method according to an exemplary embodiment of the present invention. Referring to FIG. 10, the block encryption method proceeds as follows. As described above, a temporary secret key (TPK) is generated based on the sequential processing (S310). The temporary secret key verification value C0 is generated from the temporary secret key TPK generated using one of the three methods described above (encryption method, hash method, synchronization method) (S320). In order to secure encryption against side channel attacks, fixed secret secret keys are not repeatedly used for a predetermined number. Using the generated temporary secret key (TPK), the message is encrypted so that the internal state value is continuously changed, and an authentication code is generated (S330). This time, I will explain the password authentication scheme that is designed based on the TPK table for session keys and the TPK table for nonce columns. Here, the nonce column is used to generate a mask column to protect the session key. Specifically, a mask value is used to protect input / output information of an encryption primitive using a session key. Examples of cryptographic primitives include block ciphers, compression functions, substitution functions, and tweakable block ciphers.

FIG. 11 is a diagram illustrating a block ciphering operation for explaining a cipher authentication method according to an exemplary embodiment of the present invention. FIG. In FIG. 11, it is assumed that a modified offset code book (OCB) mode is used for convenience of description. Referring to FIG. 11, when a message M having an arbitrary length is input, the message M is divided into block size units of a block cipher and expressed as M = M1 || M2 || ... || Mt. do. In this case, the size of the last unit message Mt may be selected from any value between 1 and the block size.

12 is a diagram illustrating a method of generating a mask train from a temporary secret nonce. Where Const is a fixed constant value. In the present invention, the same Const in different drawings is not the same constant value. For convenience, we write Const to mean a fixed constant. The same applies to the rest of the constant values, such as Const '. Referring to FIG. 12, the mask values Z1, Z2,... Generated from the temporary secret nonce N are used to protect the shared secret key K from side channel attacks in cryptographic authentication in FIG. 11. By using different random mask values (Z1, Z2, ...) each time, the attacker can thoroughly hide the I / O information of the block cipher during the encryption authentication process. Therefore, the shared channel K value used for the block cipher by the subchannel attacker can be protected. K may be a session key value. The nonce and session key values can be maintained in a table like the TPK table generation method. In the case of the decryption verification process, only the temporary secret key used in the TPK table can be used to provide strong security against various side channel attacks.

Then, by performing encryption and authentication as shown in FIG. 11, an encryption code C (= C0 || C1 || ... || Ct) and an τ bit value are generated. In FIG. 11, a hash function based method is used when C0 occurs. Similarly, encryption-based, synchronization-based schemes may be used. The shared key K is defined as the shared key between the two cryptographic modules 120 and 220, and Checksum = M1 xor M2 xor ... xor (Mt || 0 *).

Unlike the general OCB mode, the method illustrated in FIG. 11 takes a method of generating mask values randomly as shown in FIG. 12 to provide strong safety against side channel attacks. In addition, in FIG. 11, a mask value is also applied to the output of the block cipher when the last authentication code T value is generated to protect the shared key or session key K used. In addition, it is possible to provide safety against various side channel attacks by inducing only valid temporary secret values in the TPK table to be used in the decryption verification process. In conclusion, the modified OCB mode shown in FIG. 11 may provide strong safety against side channel attacks.

FIG. 13 is a diagram illustrating a case where the checksum shown in FIG. 11 is changed to Checksum = a1 xor a2 xor ... xor at xor (Mt || 0 *).

FIG. 14 is a diagram illustrating an example of changing a last message block processing method and a checksum illustrated in FIG. 11. FIG. 14 has a difference in the method of generating a checksum and processing of the last message block compared to that shown in FIG. When a message of arbitrary length (M) is entered, it is written as M || 10 * = M1 || M2 || ... || Mt using 10 * padding. Then, by performing encryption and authentication as shown in FIG. 14, an encrypted message C (= C0 || C1 || ... || Ct) and an authentication code T having a τ bit value are generated. In this case, Checksum = a1 xor a2 xor ... xor at. Here we generate a checksum with the values of ai, not the message block.

FIG. 15 is a diagram illustrating an example of changing a mask value applying method when processing the last message block illustrated in FIG. 14. Referring to FIG. 15, a mask value is defined as a value cyclically shifted using a constant value constant in the last message block shown in FIG. 14. The constant must not be zero or a multiple of the block size. As such, applying a different mask value when processing the last message block provides security against counterfeit attacks. Similarly, mask values can be changed for other structures.

FIG. 16 is a diagram illustrating an example of a change to a case where the additional information shown in FIG. 14 is to be authenticated together. Referring to FIG. 16, a method of generating a cipher text and an authentication code in a case where additional information A is included in comparison with FIG. 14 is illustrated. When the additional information is referred to as A, first, A is padded. After padding, the size of A should be a multiple of the block size. For convenience of explanation, when the padding method is pad, it is assumed that the size after padding is expressed as a j block, such as pad (A) = A1 || ... || Aj. For example, a 10 * padding method may be used as the padding method. And checksum = α1 xor ... xor αj xor a1 xor a2 xor ... xor at. At this time, a cipher text and an authentication code are generated. That is, the additional information A does not change the size of the cipher text, but only affects the generation of the authentication code. That is, an encrypted message C (= C0 || C1 || ... || Ct) and an authentication code T having a τ bit value are generated. In a similar manner, the additional information may be extended to other cases.

17 is a diagram illustrating an example of a method of updating a key of every block cipher without applying a mask value according to an embodiment of the present invention. Where Const and Const 'are different constant values. Referring to FIG. 17, unlike the above-described schemes, the key value used for the block cipher is updated every time without using mask values. When a message M of arbitrary length is input, the message M is split into block cipher block size units and written as M = M1 || M2 || ... || Mt. At this time, the size of the last Mt may take any value between 1 and the block size. Then, by performing encryption and authentication as shown in FIG. 14, an encrypted message C (= C0 || C1 || ... || Ct) and an authentication code T having a τ bit value are generated. Checksum = M1 xor M2 xor ... xor (Mt || 0 *).

FIG. 18 is a diagram illustrating an example of a change to a case where the additional information shown in FIG. 17 is to be authenticated together. Referring to FIG. 18, it is shown how the additional information illustrated in FIG. 17 may be processed. At this time, the checksum is defined as Checksum = α1 xor ... xor αj xor M1 xor M2 xor ... xor (Mt || 0 *).

FIG. 19 is a diagram illustrating an example of updating a key by using a temporary secret value when processing the last checksum illustrated in FIG. 17. Referring to FIG. 19, it is shown that the block cipher key is updated by using a temporary secret nonce (N) during the last checksum processing shown in FIG. 17. Similarly, other ways can be changed.

20 shows generating a mask value before each block cipher operation shown in FIG. 19 by using a key value of the block cipher. A checksum is generated by using the values of the plain text and the mask value after the XOR operation, not the checksum from the plain text itself. At this time, the checksum is defined as Checksum = a1 xor a2 xor ... xor at. When additional information A is added, it can be defined similarly to the above.

21 is a flowchart illustrating a decryption verification operation according to an embodiment of the present invention. 10 to 21, the decoding verification operation is as follows.

The encrypted message C and the authentication code T are input to the encryption module 240 (see FIG. 1) (S410). It is determined whether the temporary secret key TPK corresponding to the encrypted message C or the authentication code T is valid (S420). As described in the above-described decryption step, it is determined whether the temporary secret key (TPK) corresponding to C0 has been repeatedly used for a limited number of times. If the temporary secret key (TPK) is valid, the authentication code (T) is verified, and the decryption operation on the encrypted message (C) is performed (S440), while the temporary secret key (TPK) is not valid. If not, verification of the authentication code (T) is not in progress or the decryption operation for the encrypted message (C) is stopped (S445). That is, if the temporary secret key TTP has already been used for a limited number of times, the verification code T verification operation or decryption operation is immediately stopped.

Substitution-based encryption / decryption + authentication scheme

FIG. 23 is a diagram illustrating an example of designing an encryption authentication scheme based on prefix free message padding based on a substitution function according to an embodiment of the present invention. The substitution function-based encryption authentication and decryption verification process using the authentication method of the present invention are as follows. First, the password authentication process proceeds as follows. By performing the sequential processing in the same manner as described above, the temporary secret keys (Ni, Ni ', i are integers) are sequentially generated from the shared key K by using the substitution function P as shown in FIG. 22. do. Thereafter, as described above, the verification key C0 is generated similarly, thereby protecting the temporary secret key TPK. Afterwards, the encryption process is performed so that the internal state value is continuously changed by using a temporary secret key (TPK) generated to secure side channel attacks. That is, in the case where the shared key, session key, or temporary secret key are not repeatedly used in the base cryptographic primitive (here, substitution function or compression function), the reverse operation is performed by hiding a part or all of each input / output of the inner primitive. It also prevents attackers from knowing about forward operations. This prevents an attacker from obtaining the shared key, session key, or temporary secret key used.

FIG. 23 is a diagram illustrating an example of designing an encryption authentication scheme based on arbitrary reversible message padding based on a substitution function according to an embodiment of the present invention. Referring to FIG. 23, after the padding method pad is applied to process a message M having an arbitrary length, pad (M) = M1 || M2 || ... || Mt is expressed. In particular, the padding method pad must be prefix-free for safety reasons. This means that for any two different messages M, M ', pad (M) should never be a prefix of pad (M'). As shown in FIG. 18, C (= C0 || C1 || ... || Ct) and an τ bit value are generated for the message M.

24 and 25 are diagrams exemplarily illustrating any reversible padding methods in which the message padding method shown in FIG. 23 is not prefix free.

FIG. 26 is a view illustrating a method of changing an authentication code value having an arbitrary length to output additional information shown in FIG. 14. Similarly, Figs. 25 and 26 may also be changeable.

Next, the substitution function-based decoding process proceeds as follows. First, the temporary secret key verification value C0 is used to determine whether the temporary secret key TPK corresponding to the verification value C0 has been previously used. After verifying that the temporary secret key TPK has not been repeatedly used, the temporary secret key TPK is calculated, and a decryption operation and an authentication code verification operation on the input encrypted message C are performed. If the temporary secret key TPK corresponding to the verification value C0 is invalid, the decryption operation and the authentication code verification operation are immediately stopped.

Compression Function Based Encryption / Authentication

The compression function based encryption scheme is performed very similarly to the substitution function based scheme. 27 is a diagram illustrating an example of generating temporary secret nonce (Ni, Ni ', Ni' ') by a sequential processing method using a compression function f according to an embodiment of the present invention. Referring to FIG. 27, temporary secret keys Ni, Ni ', and Ni' 'are sequentially generated from the shared key K using the compression function f. The generated temporary secret keys Ni, Ni ', and Ni' 'are protected as described above, and an encryption operation and an authentication code are generated using the temporary secret keys.

FIG. 28 is a diagram illustrating an example of designing an encryption authentication scheme based on prefix free message padding based on a compression function f according to an embodiment of the present invention. Referring to FIG. 28, after applying a padding method pad to process a message M of an arbitrary length, it is written as pad (M) = M1 || M2 || ... || Mt. In particular, the padding method pad should be prefix-free for safety reasons. This means that for any two different messages M, M ', pad (M) should never be a prefix of pad (M'). For the input message M, C (= C0 || C1 || ... || Ct) and an τ bit value are generated.

29 and 30 show an arbitrary reversible padding method in which the message padding method shown in FIG. 28 is not prefix free. On the other hand, as shown in Figure 27, it can be changed to output an authentication code value of any length in the additional information in Figures 28, 29, and 30.

On the other hand, the temporary secret key (TPK) verification operation and thus decryption and authentication operation are similar to that of the substitution function.

About message authentication method

The message authentication operation proceeds similarly to the message encryption operation.

31 is a diagram illustrating a CBC MAC (cipher block chaining message authentication code) according to an embodiment of the present invention. Since the nonce value is not applied to the CBC MAC, the secret key value may be exposed in all block cipher operations. Therefore, a masking process is required so that the block cipher secret value is changed each time or the block cipher input / output value is not exposed as shown in the various examples.

32 illustrates a case where a masking process according to an embodiment of the present invention is applied. The CBC MAC value is defined from T, but in order to protect the nonce in the manner described above, C = H (N) and T = H '(N) for the temporary secret value (N) using the hash functions H and H'. Perform xor X (where X is the output of the last block cipher and H '(N) is used as the mask value) and take C || T as the final MAC value.

33 is a diagram illustrating a one-key MAC (OMAC) according to an embodiment of the present invention. Since OMAC does not apply nonce values like CBC MAC, secret key values can be exposed in all block cipher operations. Therefore, a masking process is required so that the block cipher secret value is changed every time or the block cipher input / output value is not exposed. Specifically, the OMAC may be modified in the manner described with reference to FIG. 33. And instead of applying fixed secret values H _L (Cst1) and H _L (Cst2) to the last block code input value part, for example, H (Cst1 || N) and H (Cst2 || N) Can be used as a mask value of the last block cipher I / O value, using fixed constant values Cst1 and Cst2 instead of secret value (L). In order to protect the temporary secret key (N) in the manner described above, H (N) and H '(N) are performed and taken as C || T as the final authentication code value in the same manner. In this case, the nonce and the shared key value may be simultaneously entered into the H input value, and the nonce may be encrypted using the shared key K instead of hashing the temporary secret key TPK.

34 is a diagram illustrating a parallelizable MAC (PMAC). Referring to Fig. 34, it is not safe because L is a fixed value. Therefore, L value should be modified. Similarly to the method described above, (N, H (N)) is generated, and C = H (N). In the above-described manner, N is used to generate L masks or different mask values for each block to protect input values of the block cipher. In addition, in the above-described manner, when the last authentication code value is generated, a mask value should be applied to the output value of the block password.

Let's take a look at HMAC. When the key is K, the message is M, and T is the authentication code value, it is expressed as T = HMAC (K, M). In this case, when the modification of the present invention, for example, when C = H (N) and T = HMAC (N, M), it is defined as C || T as the final authentication code value for M.

The authentication code verification operation is performed according to the result after verifying that the temporary secret key (TPK) is not used repeatedly.

Specific cryptographic operation using temporary secret key table

35 is a diagram exemplarily illustrating an encryption / decryption operation using a temporary secret key table (TPK Table) according to an embodiment of the present invention. Assume that the temporary secret key table is shared between two cryptographic modules (A, B). As shown in FIG. 35, it is assumed that the temporary secret key table includes a plurality of entries, each entry consisting of a nonce value and its hash value.

The encryption / decryption operation proceeds as follows. The encryption module A (eg, 120 of FIG. 1) selects any one of a plurality of entries of the temporary secret key table for the encryption operation (①). In the following description, it is assumed that the selected entry is (N3, C0_3) for convenience of description. The cryptographic module A encrypts the message using the nonce value N3 contained in the selected entries N3, C0_3. The encrypted message is then sent to the cryptographic module B (eg, 220 of FIG. 1). At this time, the cryptographic module B verifies whether a part of the encrypted message, that is, the verification value C0_3 corresponding to the nonce value N3 selected in the encryption operation, is included in the entries existing in the temporary secret key table ( ②). If the temporary secret key TPK is verified to be valid, the encryption module B proceeds to decrypt the encrypted message using this (③).

On the other hand, the temporary secret key table may further include an index to facilitate the search of the encrypted nonce value.

36 is a diagram illustrating a temporary secret key table according to an embodiment of the present invention. Referring to FIG. 36, a temporary secret key table may be composed of a plurality of entries consisting of an index, a nonce value, and a hash value (or a verification value) thereof.

The following describes how to share a temporary secret key table between cryptographic modules A and B. In FIG. 36, two cryptographic modules A and B each generate 10 entries from the shared key K for convenience of description. That is, the first entry is (1, N1, C0_1 = H (N1)), and the second entry is (2, N2, C0_2 = H (N2)). Occurs up to the tenth entry (10, N10, C0_10 = H (N10)). Then, the following table is generated. At this time, the table cannot know the remaining values except indexes except for the two cryptographic modules A and B.

As described above, when the temporary secret key table sharing is completed, the two cryptographic modules (A, B) can start communication. The cryptographic data (C) obtained by performing a cryptographic operation using N values, which are temporary secret values, is transmitted to the counterpart according to a protocol defined between the two electronic devices. The following describes the case where A sends to B. At this time, the encryption operation or the decryption operation uses N values with small indexes. A generates the encrypted data C using the temporary secret value Ni used at any point in time. Then, the entry (i, Ni, C0_i) used in the temporary secret key table is deleted and filled with the new index. In this case, instead of updating the entry every time, the entry may be performed at regular intervals, and the search time may be shortened by sorting the entries using the verification value C0 during the update.

A sends the verification value C0_i corresponding to the nonce value Ni to the B together with the encrypted data C. FIG. The index i value is not sent together. The reason is that i is an index value, so that the attacker can easily infer and send the attacker to (i, C0 ') by pretending to be A, then B is the verification value (C0_i) and C0_i' corresponding to Ni corresponding to i It will verify that it is the same. Or, it is checked whether the hash value of Ni is equal to the verification value C0_i '. If an attacker repeatedly asks about the same i value, there is a risk that the Ni or C0_i value will be exposed by side channel attacks such as template attacks.

Since the present invention does not send the index i value, B can check whether there is a verification value C0_i without knowing the index value i in its TPK table. If C0_i is missing, no further cryptographic operations are performed. If there is a C0_i value in the TPK table, the cryptographic operation is performed using Ni. Then, if there is an entry (j, Nj, C0_j) for all js less than or equal to i in B's TPK table, it is deleted and filled with new entries. In this case, instead of updating the entry every time, the entry may be performed at regular intervals, and the search time may be shortened by sorting the entries using the verification value C0 during the update.

On the other hand, even if B wants to send encrypted data to A, it can proceed in the same way as above.

37 is a diagram exemplarily illustrating a method for adding an entry of a temporary secret key table according to an embodiment of the present invention. Referring to FIG. 37, it is assumed that the first nonce N1 is used for an encryption operation or a decryption operation. At this time, the entries N1 and CO_1 used are invalidation data in the temporary secret key table. The cryptographic module can then add a new entry consisting of a new nonce (Nk + 1) and its hash value (CO_k + 1) to the temporary secret key table.

Meanwhile, the method for adding an entry of the temporary secret key table shown in FIG. 37 is merely an embodiment. The method of adding an entry of the temporary secret key table of the present invention can be implemented in various ways. The present invention can be implemented to update the temporary secret key table if the number of entries used in the temporary secret key table is greater than or equal to a predetermined number.

The schemes introduced in FIGS. 35 to 37 may be similarly used for various encryption operations such as encryption, decryption verification, authentication code generation and verification, as well as encryption and decryption.

38 is a diagram illustrating a temporary secret key table update method according to an embodiment of the present invention. Referring to FIG. 38, k entries may be newly generated when a predetermined condition is satisfied. Here, the predetermined condition may be whether the number of entries used for the encryption / decryption operation is equal to or greater than the predetermined number.

A general cryptographic system is implemented in such a way that a counterpart calculates a temporary secret key value by performing a cryptographic operation by passing a counter to the counterpart. At this time, the counter value does not decrease and increases. First, verify that the count value is valid, and then perform cryptographic operations. If the counter value is changed, the temporary secret key value corresponding to each count value is also updated, thereby providing strong security against side channel attacks. However, the cryptographic operation based on the counter value has the advantage that it can be used to shorten the search time and the small memory, etc. The reason is that the counter value does not decrease and increases, so even if a secret counter value is used, a legitimate counter value can be easily derived. This makes it difficult to verify whether a counter value is generated by a legitimate user or by an attacker. This requires further verification that the counter is generated by a legitimate user. However, these additional verification procedures are vulnerable to resource-wasting attacks such as DoS attacks, which can significantly reduce battery life, especially for battery-based cryptographic operations. In addition, repeated use of cryptographic operations corresponding to the same counter value can be vulnerable to side channel attacks such as template attacks.

Another cryptographic system is implemented to perform decryption without limiting the number of random ciphertexts, while providing security for side channel attacks without the need to maintain counter values. To this end, a method of adding a process of authenticating each message block is presented. However, this repeated authentication process is inefficient in an environment where communication efficiency is important, and in a battery-based environment, energy consumption increases, which makes it difficult to use.

An encryption system according to an embodiment of the present invention can maximize communication efficiency and minimize energy consumption. The cryptographic system of the present invention is implemented not to send counter values that are easily inferred in the future to the counterpart, but only to the counterpart, such as hash values, to be validated before the cryptographic operation begins. Unlike conventional methods, it does not use counters, so it provides security for template attacks and validates before the start of cryptographic operations. Therefore, it can efficiently detect DoS attacks.

In addition, the cryptographic system of the present invention may specifically perform encryption and decryption and authentication to be safe from side channel attacks. The present invention can be applied to various cryptographic operations such as authentication code generation, digital signature, key authentication, key exchange, etc. The present invention has shown the invention and specific embodiments thereof, and includes all techniques that can be easily inferred therefrom. do.

On the other hand, the content of the present invention described above is only specific embodiments for carrying out the invention. The invention will include not only specific and practically available means per se, but also technical ideas as abstract and conceptual ideas that may be utilized in future technology.

The present invention is applicable to any device that performs cryptographic operations.

Claims (20)

1. A decryption method of an electronic device having an encryption module, comprising:

   Receiving a message encrypted by a temporary secret key;

   Determining whether the temporary secret key is valid based on whether an entry consisting of the temporary secret key and the verification value of the temporary secret key exists in the temporary secret key table of the cryptographic module; And

   If the temporary secret key is invalid, not decrypting the encrypted message.
2. The method of claim 1,

   And if the temporary secret key is valid, decrypting the encrypted message.
3. The method of claim 1,

   Determining whether the temporary secret key is valid,

   If the entry was used in a previous decryption operation, determining that the temporary secret key is invalid.
4. The method of claim 1,

   Determining whether the temporary secret key is valid,

   Determining that the temporary secret key is invalid if the number of times the entry has been used in a previous decryption operation is greater than or equal to a predetermined value.
5. The method of claim 1,

   And the temporary secret key table includes a plurality of entries consisting of an index, a temporary secret key, and an encrypted value of the temporary secret key.
6. The method of claim 5,

   Deleting from the temporary secret table an entry for which a temporary secret key is invalid among the plurality of entries; And

   Adding a new entry to the temporary secret table, the new entry consisting of a new index, a new temporary secret key corresponding to the new index, and a verification value of the new temporary secret key.
7. The method of claim 5,

   Determining from the temporary secret table whether the number of entries in which the temporary secret key is invalid is greater than or equal to a predetermined value;

   Updating the temporary secret table when the number of invalid entries is greater than or equal to the predetermined value.
8. The method of claim 1,

   And receiving an authentication code generated by the temporary secret key and the message.
9. The method of claim 8,

   Stopping the verification operation for the authentication code when the temporary secret key is invalid; And

   And when the temporary secret key is valid, performing a verification operation on the authentication code.
10. The method of claim 9,

    And not decrypting the encrypted message when a verification operation on the authentication code fails.
11. The method of claim 9,

    Decrypting the encrypted message when the verification operation on the authentication code is successful.
12. A temporary secret key manager that receives a message encrypted with a temporary secret key having a limit on the number of times of use, and determines whether the temporary secret key is valid based on whether a verification value corresponding to the temporary secret key exists in the temporary secret key table ; And

    And a decryption unit that does not decrypt the encrypted message if the temporary secret key is invalid.
13. The method of claim 12,

    And the temporary secret key manager generates another temporary secret key.
14. The method of claim 12,

    The cryptographic module includes an encryption unit for encrypting the message with another temporary secret key.
15. The method of claim 14,

    The cryptographic module uses a message authentication code and cryptographic primitive function.
16. The method of claim 15,

    The message authentication code is generated to authenticate a message and the head information of the message.
17. In the encryption method of an electronic device having a cryptographic module:

    Generating a plurality of entries consisting of a temporary secret key having a limit on the number of uses and a verification value of the temporary secret key;

    Selecting any one of the plurality of entries;

    Encrypting the message using the temporary private key of the selected entry; And

    Generating an authentication code using the used temporary secret key and the message.
18. The method of claim 17,

    And the temporary secret key is generated based on sequential processing.
19. The method of claim 17,

    And the temporary secret key is protected using an encryption operation, a hash function, or a synchronization operation.
20. The method of claim 17,

    Transmitting the verification value and the encrypted message to another cryptographic module.

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