Proxy Re-encryption Scheme Based on SK Identity Based Encryption

The concept of proxy re-cryptography comes from the work of Blaze,Bleumer, and Strauss in 1998\cite{Blaze:98}. The goal of proxy re-encryption is to securely enable the re-encryption of ciphertexts from one key to another, without relying on trusted parties. In 2007, Matsuo proposed the concept of four types of proxy re-encryption schemes: CBE to CBE, IBE to CBE, CBE to IBE and IBE to IBE\cite{Matsuo:07}. Now CBE to IBE and IBE to IBE proxy re-encryption schemes are being standardized by IEEEP1363.3 working group\cite{P1363.3:08}. One feature of their schemes is that they are all based on BB1 identity based encryption\cite{BB04a}. We reconsider the problem of constructing proxy re-encryption based onSK identity based encryption. Surprisingly, if we consider the help of PKG, then it is easy to construct proxy re-encryption based on SK identity based encryption. Interestingly , our proxy re-encryption scheme even can achieve CCA2 secure, which makes it is unique.