Add signature module

Because things other than transactions can be signed.

src/signature.rs

@@ -0,0 +1,30 @@
+//! The `signature` crate provides functionality for public and private keys
+
+use generic_array::GenericArray;
+use generic_array::typenum::{U32, U64};
+use ring::signature::Ed25519KeyPair;
+use ring::{rand, signature};
+use untrusted;
+
+pub type PublicKey = GenericArray<u8, U32>;
+pub type Signature = GenericArray<u8, U64>;
+
+/// Return a new ED25519 keypair
+pub fn generate_keypair() -> Ed25519KeyPair {
+    let rng = rand::SystemRandom::new();
+    let pkcs8_bytes = signature::Ed25519KeyPair::generate_pkcs8(&rng).unwrap();
+    signature::Ed25519KeyPair::from_pkcs8(untrusted::Input::from(&pkcs8_bytes)).unwrap()
+}
+
+/// Return the public key for the given keypair
+pub fn get_pubkey(keypair: &Ed25519KeyPair) -> PublicKey {
+    GenericArray::clone_from_slice(keypair.public_key_bytes())
+}
+
+/// Verify a signed message with the given public key.
+pub fn verify_signature(peer_public_key_bytes: &[u8], msg_bytes: &[u8], sig_bytes: &[u8]) -> bool {
+    let peer_public_key = untrusted::Input::from(peer_public_key_bytes);
+    let msg = untrusted::Input::from(msg_bytes);
+    let sig = untrusted::Input::from(sig_bytes);
+    signature::verify(&signature::ED25519, peer_public_key, msg, sig).is_ok()
+}