I am looking for a way to have a 'did it expired' key.
There's a similar question here, but I have to prevent reusing of the 'did it expired' signature .
A possible solution would be a two one-way functions f,g such that-
- Faythe generate
key=f(private key,some date)and send it to Alice.
- Alice send
- Bob can verify that the message is up to date with the public key.
I thought of doing this with the Yao's Millionaires' Problem saying Alice has a signed value which only Bob can decrypt, but couldn't figure how to extend it.
Can Someone help me find f,g or perhaps a better idea?