Divisible On-line/Off-line Signatures

On-line/Off-line signatures are used in a particular scenario where the signer must respond quickly once the message to be signed is presented. The idea is to split the signing procedure into two phases: the off-line and on-line phases. The signer can do some pre-computations in o-line phase before he sees the message to be signed. In most of these schemes, when signing a message m, a partial signature of m is computed in the o-line phase. The authors call this part of signature the off-line signature token of message m. In some special applications, the off-line signature tokens might be exposed in the off-line phase. For example, some signers might want to transmit off-line signature tokens in the off-line phase in order to save the on-line transmission bandwidth.