In 1998, at Eurocrypt, a novel primitive, called Proxy Re-Encryption (PRE) was introduced by Blaze, Bleumer and Strauss [1]. In the given concept, a delegator computes re-encryption key and gives it to the semi trusted proxy. Then proxy can convert a message, enciphered with Alice’s public key into a message, enciphered with Bob’s public key without knowing the message. Upto best our knowledge, we have proposed the first unidirectional PRE scheme, which is noninteractive and based on lattice based identity based cryptosystem. In this scheme a trapdoor function is used for lattices, which is proposed by Micciancio and Peikert [2]. It is simple, efficient, strong and easy to implement compared to [3]. In 2013, Wang et al.[4, 5] introduced a new primitive: PRE${}^{+},$ which is similar to the conventional PRE except that, in PRE${}^{+}$ scheme encryptor computes re-encryption keys. Here encryptor is the delegator. We have also constructed a lattice identity based unidirectional PRE${}^{+}$ scheme.

1998年，在Eurocrypt上，Blaze，Bleumer和Strauss提出了一种称为代理重新加密（PRE）的新颖原语[1]。在给定的概念中，委托者计算重新加密密钥并将其提供给半信任代理。然后，代理可以将使用Alice的公钥加密的消息转换为使用Bob的公钥加密的消息，而无需知道该消息。据我们所知，我们提出了第一个单向PRE方案，该方案是非交互式的，基于基于格的基于身份的密码系统。在该方案中，陷阱门函数用于格，这是Micciancio和Peikert [2]提出的。与[3]相比，它简单，高效，强大且易于实施。2013年，Wang等人[4，5]引入了一个新的原语：PRE${}^{+}，$ 与传统的PRE相似，除了在PRE中${}^{+}$方案加密器计算重新加密密钥。这里，加密器是委托者。我们还构造了基于晶格身份的单向PRE${}^{+}$ 方案。