In 1998, Blaze, Bleumer, and Strauss proposed new kind of cryptographic primitives called proxy reencryption (PRE) and proxy re-signature (PRS) [2]. In proxy re-encryption, a proxy can transform a ciphertext computed under Alice’s public key into one that can be opened under Bob’s decryption key. In proxy re-signature, a proxy can transform a signature computed under Alice’s secret key into one...

Proxy signature is a special signature which provided the signer can delegate his signing capability to others. The proxy signature provides that the original signer can delegate his signing permission to a proxy signer, and the proxy signer can replace the original signer to sign the message. In this paper, we propose a proxy signature scheme based on ideas from classical proxy signature schem...

Identity-based (ID-based) public key cryptosystem can be a good alternative for certificate-based public key setting, especially when efficient key management and moderate security are required. In a (t, n) threshold proxy signature scheme, the original signer delegates the power of signing messages to a designated proxy group of n members. Any t or more proxy signers of the group can cooperati...

A Cloud data storage system consists of collection of storage servers over the internet which provides long term storage services. The data stored in a third party’s cloud system may cause serious concern over data confidentiality. To keep sensitive user data confidential against un-trusted servers and to provide security, access control in cloud there are some cryptographic techniques speciall...

A threshold proxy signature scheme allows any or more proxy signers to cooperatively sign messages on behalf of an original signer, but or fewer proxy signers cannot. In this paper, in order to adapt to some practical applications, by a modification of Hu threshold proxy signature, we propose a novel secure variation of proxy signature scheme called general proxy signature scheme. This scheme h...