Optimistic blinded-key signatures

If autonomous mobile agents are to be used in electronic commerce environments, they must be able to sign contracts and payment orders without the need to contact their owners. As agents execute in untrusted environments, it is assumed that any information they carry can be read by a malicious host; thus, it is unwise to include secrets, such as private keys, in such agents. Sander and Tchudin proposed the concept of undetachable signatures to solve this problem, but gave no practical manifestation for it. Ferreira and Dahab's blinded-key-signatures were proposed as a practical implementation of Sander and Tchudin's idea, but require the intervention of an online TTP (trusted third party). Here, we propose optimistic blinded-key signatures, which require a TTP only in a disputed transaction.