Merge pull request #55 from sigp/validator_induction

[BLOCKED] Validator induction

beacon_chain/utils/bls/Cargo.toml

@@ -5,3 +5,4 @@ authors = ["Paul Hauner <paul@paulhauner.com>"]
 
 [dependencies]
 bls-aggregates = { git = "https://github.com/sigp/signature-schemes" }
+hashing = { path = "../hashing" }

beacon_chain/utils/bls/src/lib.rs

@@ -1,4 +1,5 @@
 extern crate bls_aggregates;
+extern crate hashing;
 
 pub use self::bls_aggregates::AggregateSignature;
 pub use self::bls_aggregates::AggregatePublicKey;
@@ -8,3 +9,21 @@ pub use self::bls_aggregates::PublicKey;
 pub use self::bls_aggregates::SecretKey;
 
 pub const BLS_AGG_SIG_BYTE_SIZE: usize = 97;
+
+use hashing::proof_of_possession_hash;
+
+/// For some signature and public key, ensure that the signature message was the public key and it
+/// was signed by the secret key that corresponds to that public key.
+pub fn verify_proof_of_possession(sig: &Signature, pubkey: &PublicKey)
+    -> bool
+{
+    let hash = proof_of_possession_hash(&pubkey.as_bytes());
+    sig.verify_hashed(&hash, &pubkey)
+}
+
+pub fn create_proof_of_possession(keypair: &Keypair)
+    -> Signature
+{
+    let hash = proof_of_possession_hash(&keypair.pk.as_bytes());
+    Signature::new_hashed(&hash, &keypair.sk)
+}

beacon_chain/utils/hashing/src/lib.rs

@@ -6,3 +6,12 @@ pub fn canonical_hash(input: &[u8]) -> Vec<u8> {
     let result = blake2b(64, &[], input);
     result.as_bytes()[0..32].to_vec()
 }
+
+pub fn proof_of_possession_hash(input: &[u8]) -> Vec<u8> {
+    let result = blake2b(64, &[], input);
+    let mut hash = result.as_bytes()[32..64].to_vec();
+    // TODO: this padding is not part of the spec, it is required otherwise Milagro will panic.
+    // We should either drop the padding or ensure the padding is in the spec.
+    hash.append(&mut vec![0; 18]);
+    hash
+}