条件型非对称跨加密系统的代理重加密方案

为了减轻云应用中移动设备解密的负担，利用基于身份的广播加密（IBBE）、基于身份的加密（IBE）、基于身份的条件型广播代理重加密方案，提出了多条件型非对称跨加密系统的代理重加密方案。该方案允许发送方将信息加密成IBBE密文，一次性发送给多个接收方，其中任一接收方又可以授权给代理者一个多条件型的重加密密钥，代理者利用该多条件型重加密密钥，能将符合多个条件的原始密文重加密成一个新的接收方可以解密的IBE密文。该方案实现了从IBBE加密系统到IBE加密系统的非对称代理重加密，而且代理者可以根据条件将最初的原始密文进行重加密，避免了不需要进行重加密的原始密文被代理者重加密，提高了代理者重加密的效率，同时节约了接收方获悉正确明文的时间。

Proxy re-encryption scheme based on conditional asymmetric cross-cryptosystem

In order to reduce the decryption burden of the mobile device in cloud application, using Identity-Based Broadcast Encryption (IBBE) scheme, Identity-Based Encryption (IBE) scheme and conditional identity-based broadcast proxy re-encryption scheme, an asymmetric cross-cryptosystem proxy re-encryption scheme with multiple conditions was proposed. In this scheme, the sender is allowed to encrypt information into IBBE ciphertext, which can be sent to multiple recipients at a time. Anyone of the receivers can authorize a multi-condition re-encryption key to the proxy to re-encrypt the original ciphertext which meets the conditions into the IBE ciphertext that a new receiver can decrypt. The scheme realizes asymmetric proxy re-encryption from IBBE encryption system to IBE encryption system and allows the proxy to re-encrypt the original ciphertext according to the conditions, which avoids the proxy to re-encrypt the unnecessary original ciphertext. The scheme not only improves the re-encryption efficiency of the proxy, but also saves the time of the receiver to get the correct plaintext.