Modified forward secure signatures for mobile computing applications

Messages transmitted in untrusted mobile environments may be secured by signing them using digital signature algorithms. forward-secure digital signatures enable the signer to guarantee the security of messages signed in the past even if his secret key is exposed today. We present a forward-secure like signature scheme with the following features: the verifier Bob can verify messages signed by Alice without himself being able to forge such signatures. If an adversary (may be service provider himself) gains access to either Bob´s (verification) key or Alice´s (present signing) key, nevertheless he cannot forge Alice´s past signatures