authentication codeの例文

例文

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1. By definition, a Message Authentication Code is " broken " if we can find a different message ( a sequence of plain-text pairs P') which produces the same tag as the previous message, P, with P \ not = P '.
2. For HMAC-MD5 the RFC summarizes that-although the security of the MD5 hash function itself is severely compromised-the currently known " " attacks on HMAC-MD5 do not seem to indicate a practical vulnerability when used as a message authentication code . ""
3. Message authentication codes ( MACs ) are much like cryptographic hash functions, except that a secret key can be used to authenticate the hash value upon receipt; this additional complication blocks an attack scheme against bare digest algorithms, and so has been thought worth the effort.
4. For a secure unforgeable message authentication code, it should be computationally infeasible to compute a valid tag of the given message without knowledge of the key, even if for the worst case, we assume the adversary can forge the tag of any message except the given one.
5. Standard techniques to prevent this, such as the use of a message authentication code can be used along with a one-time pad system to prevent such attacks, as can classical methods such as variable length padding and Russian copulation, but they all lack the perfect security the OTP itself has.