Signatures/encryption

[sp5wwp]

1. Expand the definition of the encryption subtype subfield of TYPE with AES key length indication.
2. Add definitions for ECDSA signed streams.

[lwvmobile]

Something I was considering on that, is if we use the following setup for AES, it'll let us use the crypt code we've got currently and also allow compatibility to m17-tools which still uses the hard coded 128 keylen value, since that signals enc_subtype as 0 on AES, and is also the same progression of key len values that scrambler mode uses.

subtype 0 for AES 128;
subtype 1 for AES 192;
subtype 2 for AES 256;

[sp5wwp]

Agreed! The enum in the code needs to be changed to start with 0.

[sp5wwp]

AES subtypes added to the spec doc in dce7f5e.