I tried to blind some big message using pythons RSA from Crypto.PublicKey. The problem is, even if i generate big key, like 6400 bits, key.blind() method still crushes with "message too large" error. I know, that my message can't be bigger than N in key, because every computation is in modulo N, but how can big things be blind signed then?
Just like normal signatures: first perform a cryptographic (one-way) hash over the message and blind & sign that instead of the message.
Python Crypto blinding big messages