Getting Passphrase From Encrypted and Unencrypted Secret Key

[Robert J. Hansen]

On 5/29/2014 5:07 PM, Marko Randjelovic wrote:
> If an attacker got my secret key while it wasn't encrypted (no
> passphrase) and then I put a passphrase, and then the same attacker
> gets encrypted key, can he find out my passphrase based on difference
> between non-encrypted and encrypted key?

This is considered "computationally infeasible."  That phrase means, "it
would require science-fiction technologies to do it."