This add an implementation for the EMSA-PKCS1-V1_5-ENCODE function from
RFC8017 section 9.2. The verification of this encoding is implemented by
simply encoding the message to be verified, and then comparing the two
encoded string.
The digest info for the different hash function is from RFC8017 section
9.2 notes 1. These byte sequences are actually ASN.1 encoded data,
however these are always constant for a specific hash function and can
be treated as opaque byte sequences.
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