Erlang signing and verifying hashed data, using openssh keys

signature.erl

-module(signature).
-export([test/0]).

% Looking at using Open SSH public and private keys
% for signing and verifying hashed data.

load_public_key(Filename) ->
  {ok, SshBin} = file:read_file(Filename),
  [{PubKey,_}] = public_key:ssh_decode(SshBin, public_key),
  PubKey.

load_private_key(Filename) ->
  {ok, Pem} = file:read_file(Filename),
  [Entry] = public_key:pem_decode(Pem),
  public_key:pem_entry_decode(Entry).

sign_verify(PublicKey, PrivateKey, Digest) ->
  Signature = public_key:sign(Digest, sha, PrivateKey),
  true = public_key:verify(Digest, sha, Signature, PublicKey).

test() ->
  Msg = "This is the message",
  Digest = crypto:sha(Msg),
  PublicKey = load_public_key("id_rsa.pub"),
  PrivateKey = load_private_key("id_rsa"),
  sign_verify(PublicKey, PrivateKey, Digest).