International Association for Cryptologic Research

International Association
for Cryptologic Research


Paper: Group Encryption

Aggelos Kiayias
Yiannis Tsiounis
Moti Yung
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Abstract: We present group encryption, a new cryptographic primitive which is the encryption analogue of a group signature. It possesses similar verifiability, security and privacy properties, but whereas a group signature is useful whenever we need to conceal the source (signer) within a group of legitimate users, a group encryption is useful whenever we need to conceal a recipient (decryptor) within a group of legitimate receivers. We introduce and model the new primitive and present sufficient as well as necessary conditions for its generic implementation. We then develop an efficient novel number theoretic construction for group encryption of discrete logarithms whose complexity is independent of the group size. To achieve this we construct a new public-key encryption for discrete logarithms that satisfies CCA2-key-privacy and CCA2-security in the standard model. Applications of group encryption include settings where a user wishes to hide her preferred trusted third party or even impose a hidden hierarchy of trusted parties, or settings where verifiable well-formed ciphertexts are kept in a untrusted storage server that must be prevented from both learning the content of records as well as analyzing the identities of their retrievers.
  title={Group  Encryption},
  booktitle={IACR Eprint archive},
  keywords={public-key cryptography /},
  note={ 13532 received 12 Jan 2007, last revised 19 Jan 2007},
  author={Aggelos Kiayias and Yiannis Tsiounis and Moti Yung},