Hybrid authenticated protocol Let's suppose that two entities, A and B, are establishing a secure channel and then require a mutual authentication.

A has only a RSA key pair and B has an ECDSA key pair. Both of them trust the public key of each other.

Do you feel comfortable with having A signing it's message with RSA and B signing its message with ECDSA ?

They do have an equivalent key length for both key pairs (keylength.com)
Yes, given the following conditions:


A trusts the public key of B belonging to B
B trusts the public key of A belonging to A
A trusts the signing algorithm ECDSA used by B
B trusts the signing algorithm RSA used by A
A trusts the key length of B
B trusts the key length of A


Normally, the condition 3,4 use the same algorithm, but if both A and B put trust in the other's algorithm then there is no reason not to trust the authenticity.

As you said 1,2 and 5,6 are true.