## Cryptology ePrint Archive: Report 2002/155

Secure Bilinear Diffie-Hellman Bits

Steven D. Galbraith, Herbie J. Hopkins, Igor E. Shparlinski

Abstract: The Weil and Tate pairings are a popular new gadget in cryptography and have found many applications, including identity-based cryptography. In particular, the pairings have been used for key exchange protocols. This paper studies the bit security of keys obtained using protocols based on pairings (that is, we show that obtaining certain bits of the common key is as hard as computing the entire key). These results are valuable as they give insight into how many hard-core'' bits can be obtained from key exchange using pairings.

Category / Keywords: public-key cryptography / pairings, bit security