Secret handshake protocols were recently introduced [1] to allow members of the same group to authenticate each other secretly, in the sense that someone who is not a group member cannot tell, by engaging some party in the handshake protocol, whether that party is a member of this group. On the other hand, any two parties who are members of the same group will recognize each other as members. Thus, a secret handshake protocol can be used in any scenario where group members need to identify each other without revealing their group affiliations to outsiders. The work of [1] constructed a secret handshake protocol secure under the Bilinear DiffieHellman (BDH) assumption in the Random Oracle Model (ROM). We show how to build secret handshake protocols secure under more standard cryptographic assumptions, using a novel tool of CA-oblivious public key encryption, which is an encryption scheme s.t. neither the public key nor the ciphertext reveal any information about the Certification Authority (CA) which certified the public key. We construct CA-oblivious encryptions and handshake schemes based (in ROM) on either the Computational Diffie-Hellman or the RSA assumption.
Castelluccia et al. in REF introduce the concept of CAOblivious encryption and show how to build a Secret Handshake scheme from such a primitive.
Secret Handshakes from CA-Oblivious Encryption
ASIACRYPT
Computer Science