Dual-Signatures for a Quantum-safe Future

[amogorkon]

https://learning.oreilly.com/library/view/transitioning-to-quantum-safe/9780738460680/8525ch02.xhtml#ww462412

Implement dual signing. A dual signature consists of at least two signatures on a common message. According to guidance provided by NIST, one signature is generated with a NIST-approved signature scheme as specified in FIPS 196, while the other signatures can be generated by using a different signature algorithm.
For quantum-safe, the second signature is a quantum-safe signature (CRYSTALS-Dilithium is used for IBM z16). The signatures must be parsed and verified separately; if either fails, the signature for the object fails.