# Given N and e in RSA and the ability to get signature s for any message m, can you find the value of the private key d?

Given N and e in RSA and the ability to get signature s for any message m ($$s=m^d \mod{n}$$), can you find the value of the private key d?

• Did you search on our site? Are you asking for a TextBook signature that is already insecure? Or are you asking for RSA-PSS? Note that signature requires hashing of the message since the first true Rabin Signature Scheme, May 25 '21 at 14:10
• @kelalaka on the site I found this crypto.stackexchange.com/questions/9896/… that shows how to find a signature m without d and I also found how to find N without having it initially, but I haven't found how to work out d given N and e and the ability to find the signature for any message m. The signature I'm talking about is $s=m^d\mod{n}$ and you can modify m to any value you like and receive the value of $s$ May 25 '21 at 14:12
• Nope, signature requires the private key. May 25 '21 at 14:38
• You're right I mad an error again :) I think I'm tired May 25 '21 at 14:39
• Hint: If you can find, then you can solve factorisation problem, too May 25 '21 at 14:44