Identity-Based Proxy Re-Encryption Based on LWE with Short Parameters

Proxy re-encryption (PRE) can guarantee the security of data sharing in the cloud making it important in ciphertext sharing in the cloud computing environment. Plenty of the current PRE algorithms based on the learning with errors (LWE) problem are constructed under the random oracle model or have problems such as long public parameter size, large ciphertext expansion rate, etc. We propose an identity-based PRE (IB-PRE) scheme using the LWE problem with short public parameters which can solve the mentioned challenges. Our scheme uses the blocking operation to decrease the public parameter size and a more useful trapdoor generation algorithm to reduce the trapdoor size. These two technologies improve the computational efficiency of the public key. We think that when we divide the identity id into 16 blocks, without much increase in computational overhead, the public key size can be reduced by 88.34%, and the scheme’s security level can remain unchanged. Our scheme achieves adaptive IND-ID-CPA security. It is unidirectional, collusion-resistant, and constructed under the standard model.