| 7.1 PGP makes use of the cipher feedback (CFB) mode of CAST-128, whereas most symmetric encryption applications (other than key encryption) use the cipher block chaining (CBC) mode.We have CBC: Ci = E(K, [Ci-1+ Pi]); Pi = Ci-1+ D(K, Ci) CFB: Ci = Pi + E(K, Ci-1); Pi = Ci + E(K, Ci-1) These two appear to provide equal security. Suggest a reason why PGP uses the CFB mode. | |
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