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Forward/Backward Unforgeable Digital Signature Scheme Using Symmetric-Key Crypto-System

Forward/Backward Unforgeable Digital Signature Scheme Using Symmetric-Key Crypto-System. Introduction(1/). A secure digital signature scheme should satisfy the following requirements:

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Forward/Backward Unforgeable Digital Signature Scheme Using Symmetric-Key Crypto-System

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  1. Forward/Backward Unforgeable Digital Signature Scheme Using Symmetric-Key Crypto-System Department of Computer Science and Information Engineering, National Cheng Kung University, Tainan, Taiwan, R.O.C.

  2. Introduction(1/) Computer & Internet Architecture Lab CSIE NCKU • A secure digital signature scheme should satisfy the following requirements: • Authentication: Through the verified signature, the signature receiver can verify the identity of signer and the integrity of the message. • Non-repudiation: A signer who has sent a valid signature to a receiver cannot later deny having provided that signature.

  3. Introduction(2/) Computer & Internet Architecture Lab CSIE NCKU • Unforgeability: Neither the signature receiver nor an attacker can forge a signature or change the content of a signature. The signature should not be reproducible by any other person. • Forward Unforgeability: Even if the signature key used in the scheme is compromised, then any previous signature will not be forged. • Backward Unforgeability: Even if the signature key used in the scheme is compromised, then the attacker will not be able to forge any future signature.

  4. background Computer & Internet Architecture Lab CSIE NCKU Digital signatures employ asymmetric cryptography.

  5. Proposed Signature Schemes(1/) Computer & Internet Architecture Lab CSIE NCKU

  6. Proposed Signature Schemes(2/) Computer & Internet Architecture Lab CSIE NCKU

  7. Security Analysis Computer & Internet Architecture Lab CSIE NCKU In the proposed forward unforgeable signature scheme, since the encryption key is updated in every signature transmission by using a secret random number, therefore, an attacker cannot forge any previous signature without knowing the random number.

  8. Security Analysis Computer & Internet Architecture Lab CSIE NCKU the security backbone of the proposed backward unforgeable signature scheme is based on the one-way hash function. That is, anyone cannot reconstruct the input of hash function from its hash value alone. Therefore, if the current signature key (i.e., the one-time signature key) is compromised, then the attacker will not be able to forge any future signature.

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