摘要:
An encrypted communication system, capable of performing processing with the speed higher than the conventionally achieved speed, includes an encryption device and a decryption device sharing parameters that satisfy p=3 and q=2^k (k: an integer of 2 or greater). The decryption device generates a public key and a private key using the parameters, the encryption device encrypts a plain text using the public key, and then, the decryption device decrypts the encrypted text using its own private key.
摘要:
A signature generation apparatus and a signature verification apparatus which can prevent the occurrence of norm zero vector forgery attack. The signature generation apparatus (110) includes a signature generation unit (114) which generates signature data (S) for a message (m) using a private key stored in a private key storage unit (112), and converts the format of the signature data (S) so that the first sub-element of the N sub-elements in the signature data (S) indicates 0 without changing the norm of the signature data (S). The signature verification apparatus (120) includes a signature verification unit (124) which judges whether or not the first sub-element of the N sub-elements included in the signature data (S) indicates 0, and determines the signature data (S) as unauthorized data when judging that it is not 0.
摘要:
A communication device is secure against an impersonation attack as well. The communication device secretly communicates, with an external device, target data with use of a key shared with the external device. Without being known to a third party, the communication device generates a key shared with the external device using a scheme of which security is proved. Validity of the external device is determined by authentication with use of a key dependent function that is shared with the external device and is dependent on the shared key. If the external device is determined to be valid, for secretly communicating the target data, verification data for verifying validity of the target data is generated from the target data with use of the key dependent function.
摘要:
At the time of manufacturing a DVD to be provided to a rental agent, a provider device writes an agent-rental expiry along with contents onto the DVD. At the time of renting the DVD to a user, a rental agent device writes a user-expiry onto the DVD. A DVD player acquires a current time from a time source device, and compares the current time with each of a prior time, the agent-rental expiry, and the user-rental expiry. The DVD player plays back the content only when playback conditions are met.
摘要:
There is provided a signature generation apparatus capable of preventing transcript attack on signature data. The signature generation apparatus for generating signature data for message data (i) acquires, according to a predetermined acquisition method, a private key, which is different from a private key used in a previous digital signature operation, from among a plurality of private keys generated using a key generation method of a signature scheme in which the plurality of private keys correspond to a single public key, and (ii) performs, using the acquired private key, a digital signature operation on the message data according to a signature method of the signature scheme to generate the signature data.
摘要:
To provide a content delivery system which enables a ciphertext to be reduced in size when using the ElGamal cipher. A content delivery device performs elliptic curve encryption on a content key, generates an encrypted content key that includes an x coordinate of an elliptic curve point obtained by the elliptic curve encryption, and outputs the encrypted content key. A content reception device receives the encrypted content key, and calculates a y coordinate of the elliptic curve point using the x coordinate included in the encrypted content key. The content reception device then performs elliptic curve decryption using the elliptic curve point and other information included in the encrypted content key, to generate a decrypted content key.
摘要:
A transmission apparatus performs a one-way operation on plaintext to generate a first value and transmits the first value, generates first additional information, performs an invertible operation on the plaintext and first additional information to generate connected information, encrypts the connected information using an encryption algorithm to generate ciphertext, and transmits the ciphertext. A reception apparatus receives the first value and the ciphertext, generates second additional information identical to the first additional information, decrypts the ciphertext using a decryption algorithm, which is an inverse-conversion of the encryption algorithm, to generate decrypted connected information, decrypts the decrypted connected information and the second additional information according to an inverse of the invertible operation to generate decrypted text, performs the one-way operation on the decrypted text to generate a second value, compares the first and second values, and judges that the decrypted text is valid only when the first and second values match.
摘要:
An obfuscating apparatus creates a table for inputting the same number of arguments for multiplying and squaring operations, and sets the output values of the table so that the outputs may depend on the arguments. With regard to the squaring operations, there are added and tabulated adding operations using the arguments necessary only for the multiplications, so that the number of arguments is equal to that of the multiplication operations. The outputs depend on all the arguments, so that the presence or absence of the added arguments is unknown unlike the case in which dummy arguments that are not processed are added.
摘要:
A program obfuscating device for generating obfuscated program from which unauthorized analyzer cannot obtain confidential information easily. The program obfuscating device stores original program that contains authorized program instructions and confidential process instruction group containing confidential information that needs to be kept confidential, generates process instructions which, when executed in predetermined order, provide same result, with execution of last process instruction thereof, as the confidential process instruction group, inserts the process instructions into the original program at position between start of the original program and the confidential process instruction group so as to be executed in the predetermined order, in place of the confidential process instruction group, generates dummy block as dummy of the process instructions, and inserts the dummy block and control instruction, which causes the dummy block to be bypassed, into the original program, and inserts branch instruction into the dummy block.
摘要:
A signature generation apparatus capable of preventing transcript attack on signature data is provided. The signature generation apparatus performing a digital signature operation with the use of a signature key: stores the signature key; performs the digital signature operation on signature target data with the use of the signature key to generate signature data; counts the cumulative count of digital signature operations having been performed by the signature generation unit with the use of the signature key; judges whether the cumulative count has reached a predetermined count; and inhibits the use of the signature key in the digital signature operation from then onward in a case where the judgment unit determines that the cumulative count has reached the predetermined count.