Incorrect naming for SPKI

[owlstead]

There is no such thing as a PKCS#8 public key. What is used when decoding a "PKCS#8 public key" in this library is called a "SubjectPublicKeyInfo" or "spki" for short.

The PKCS#8 only describes (possibly encrypted) private keys. As these private keys also contain a key type / algorithm they have the same role as SubjectPublicKeyInfo (this is why they don't need the algorithm description in the PEM header, i.e. PRIVATE / PUBLIC KEY instead of RSA PRIVATE / PUBLIC KEY).

I think it would be best to add a "SubjectPublicKeyInfo" or "spki" encoding / decoding format for the Import/Export keys
functionality, and explain that "pkcs8" can also be used to encode / decode formats for backwards compatibility.

The SubjectPublicKeyInfo format is specified in the X.509 specifications (which is why they are known as "X509" in Java, but I think "spki" is better and more commonplace). Of course, the BIT STRING simply contains the PKCS#1 encoded public key for RSA.