International Association for Cryptologic Research
"Proxy Re-Encryption (PRE) schemes are cryptosystems which allow a proxy who has a re-encryption key to convert a cipher-text originally encrypted for one party into a cipher-text which can be decrypted by another party. In, Hayashi et al. proposed the new security notion for PRE called ""Unforgeability of Re-encryption Keys against Collusion Attacks,"" (UFReKey-CA). They proposed the PRE schemes and claimed that their schemes meet UFReKey-CA. However, the researcher pointed out that the schemes do not meet UFReKey-CA. It is an open problem of constructing the scheme which meets UFReKey-CA."