Almost every scheme that does signing and encryption has separate keys for each (even in cases like GnuPG which pretends to have a single key). In fact, TFA ex

Almost every scheme that does signing and encryption has separate keys for each (even in cases like GnuPG which pretends to have a single key). In fact, TFA explicitly mentions an example of this causing a security problem[1]. In addition, not all public-key cryptosystems can be used to create both encryption and signing primitives[2]. [1]: https://eprint.iacr.org/2011/615.pdf https://eprint.iacr.org/2011/615.pdf [2]: https://www.cs.cornell.edu/courses/cs5430/2015sp/notes/rsa_sign_vs_dec.php https://www.cs.cornell.edu/courses/cs5430/2015sp/notes/rsa_s...