Verification of identity based signatures

A cryptographic system comprising:

• at least one signing processor device for generating a plurality of digital signatures comprising:
• a plurality of signing processor devices independently generating a plurality of identity-based digital signatures, using domain parameters P and private keys sA retrieved from a key generation centre, wherein there is a constant relationship between the private keys sA and their associated public keys A, and in which a public parameter Q common to all signatures is used together with the private key to generate each signature;
• and
• a verification system comprising:
• a first interface to receive the digital signatures, a second interface to retrieve cryptography data from a key generation centre, and a processor device for performing batch verification of all of the signatures together comprising:
• a verification processor device verifying all of the identity-based digital signatures together in a batch process by executing functions on elements of the signatures, wherein for each element the verification processor device combines values of that element for all of the signatures to provide an aggregate element, and then performs a verification function using the aggregate elements, wherein said verification function is a bilinear map which maps between aggregate elements of one or two groups to an element in one group.

A database management system comprising:

• a plurality of workstations each for generating a data record together with a digital signature of a registered user who is responsible, said digital signatures being generated according to a plurality of signing processor devices independently generating a plurality of identity-based digital signatures, using domain parameters P and private keys sA retrieved from a key generation centre, wherein there is a constant relationship between the private keys sA and their associated public keys A, and in which a public parameter Q common to all signatures is used together with the private key to generate each signature;
• and;
• a database controller for writing data record updates to a database, said records comprising update data together with a digital signature for the person responsible;
• a signature verification processor device verifying all of the identity-based digital signatures together in a batch process by executing functions on elements of the signatures, wherein for each element the verification processor device combines values of that element for all of the signatures to provide an aggregate element, and then performs a verification function using the aggregate elements, wherein said verification function is a bilinear map which maps between aggregate elements of one or two groups to an element in one group.

A cryptographic method comprising the steps of:

• a plurality of signing processors independently generating a plurality of identity-based digital signatures, using domain parameters P and private keys sA retrieved from a key generation centre;
• wherein there is a constant relationship between the private keys sA and their associated public keys A, and in which a public parameter Q common to all signatures is used together with the private key to generate each signature;
• a verification processor device verifying all of the identity-based digital signatures together in a batch process by executing functions on elements of the signatures;
• wherein for each element the verification processor device combines values of that element for all of the signatures to provide an aggregate element, and then performs a verification function using the aggregate elements;
• wherein said verification function is bilinear map which maps between aggregate elements of one or two groups to an element in one group, wherein the public parameter Q is multiplied by a randomly generated multiplier x to provide a secret component xQ of an element of each signature;
• wherein during signature generation the public parameter P is used in one element and the public component Q is used in another element.