PLAINTEXT EQUIVALENCE PROOF TECHNIQUES IN COMMUNICATION SYSTEMS

摘要

Methods aiding in proving shuffles of re-encryptions of ciphertexts and a mixnet employing such methods are disclosed. A method for compacting ciphertexts includes encrypting a plaintext using an asymmetric key encryption scheme to obtain a ciphertext, dividing the ciphertext into a plurality of partial ciphertexts, encrypting each of the plurality of partial ciphertexts using the asymmetric key encryption scheme to obtain a plurality of re-encrypted partial ciphertexts, creating a plurality of hash exponents from a digest of a cryptographic hash function taking the plurality of partial ciphertexts, the plurality of re-encrypted partial ciphertexts and a plurality of arbitrary salt values as argument of the cryptographic hash function, calculating a compacted ciphertext by multiplying all of the plurality of partial ciphertexts exponentiated by a respective one of the plurality of hash exponents, and calculating a compacted re-encrypted ciphertext by multiplying all of the plurality of re-encrypted partial ciphertexts exponentiated by a respective one of the plurality of hash exponents.