Paper 1998/010

Chameleon Hashing and Signatures

Hugo Krawczyk and Tal Rabin


We introduce CHAMELEON SIGNATURES that provide with an undeniable commitment of the signer to the contents of the signed document (as regular digital signatures do) but, at the same time, do not allow the recipient of the signature to disclose the contents of the signed information to any third party without the signer's consent. These signatures are closely related to Chaum's "undeniable signatures", but chameleon signatures allow for simpler and more efficient realizations than the latter. In particular, they are essentially non-interactive and do not involve the design and complexity of zero-knowledge proofs on which traditional undeniable signatures are based. Instead, chameleon signatures are generated under the standard method of hash-then-sign. Yet, the hash functions which are used are CHAMELEON HASH FUNCTIONS. These hash functions are characterized by the non-standard property of being collision-resistant for the signer but collision tractable for the recipient. We present simple and efficient constructions of chameleon hashing and chameleon signatures. The former can be constructed based on standard cryptographic assumptions (such as the hardness of factoring or discrete logarithms) and have efficient realizations based on these assumptions. For the signature part we can use any digital signature (such as RSA or DSS) and prove the unforgeability property of the resultant chameleon signatures solely based on the unforgeability of the underlying digital signature in use.

Available format(s)
Publication info
Published elsewhere. Appeared in the THEORY OF CRYPTOGRAPHY LIBRARY and has been included in the ePrint Archive.
Digital signaturesundeniable signaturescollision-resistant hashingchameleon signatureschameleon hashing
Contact author(s)
talr @ watson ibm com
1998-03-17: received
Short URL
Creative Commons Attribution


      author = {Hugo Krawczyk and Tal Rabin},
      title = {Chameleon Hashing and Signatures},
      howpublished = {Cryptology ePrint Archive, Paper 1998/010},
      year = {1998},
      note = {\url{}},
      url = {}
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