From d91a89ebeb653dedc2d2dceca4f646e36cb6468e Mon Sep 17 00:00:00 2001
From: Mark Spanbroek <mark@spanbroek.net>
Date: Tue, 3 Dec 2024 15:11:39 +0100
Subject: [PATCH] BLS signatures

---
 codexvalidator.nimble                   |  1 +
 codexvalidator/signatures.nim           | 31 +++++++++++++++++
 tests/codexvalidator/testSignatures.nim | 44 +++++++++++++++++++++++++
 tests/tests.nim                         |  1 +
 4 files changed, 77 insertions(+)
 create mode 100644 codexvalidator/signatures.nim
 create mode 100644 tests/codexvalidator/testSignatures.nim

diff --git a/codexvalidator.nimble b/codexvalidator.nimble
index 7ecd3bc..d379e0a 100644
--- a/codexvalidator.nimble
+++ b/codexvalidator.nimble
@@ -5,3 +5,4 @@ license = "MIT"
 
 requires "https://github.com/codex-storage/nim-mysticeti >= 0.1.0 & < 0.2.0"
 requires "https://github.com/codex-storage/nim-stint-versioned.git >= 1.0.0 & < 2.0.0"
+requires "https://github.com/mratsim/constantine#bc3845aa492b52f7fef047503b1592e830d1a774"
diff --git a/codexvalidator/signatures.nim b/codexvalidator/signatures.nim
new file mode 100644
index 0000000..e480f0c
--- /dev/null
+++ b/codexvalidator/signatures.nim
@@ -0,0 +1,31 @@
+import pkg/constantine/ethereum_bls_signatures
+import pkg/constantine/csprngs/sysrand
+
+export Signature
+
+type
+  Identity* = SecretKey
+  Identifier* = PublicKey
+
+proc random*(_: type Identity, identity: var Identity) =
+  var randomness: array[32, byte]
+  var done = false
+  while not done:
+    doAssert sysrand(randomness)
+    done = deserialize_seckey(identity, randomness) == cttCodecScalar_Success
+  setZero(randomness)
+
+func identifier*(identity: Identity): Identifier =
+  derive_pubkey(result, identity)
+
+func sign*(identity: Identity, message: openArray[byte]): Signature =
+  sign(result, identity, message)
+
+func verify*(signature: Signature, identifier: Identifier, message: openArray[byte]): bool =
+  verify(identifier, message, signature) == cttEthBls_Success
+
+func `==`*(a, b: Identifier): bool =
+  pubkeys_are_equal(a, b)
+
+func `==`*(a, b: Signature): bool =
+  signatures_are_equal(a, b)
diff --git a/tests/codexvalidator/testSignatures.nim b/tests/codexvalidator/testSignatures.nim
new file mode 100644
index 0000000..77f1489
--- /dev/null
+++ b/tests/codexvalidator/testSignatures.nim
@@ -0,0 +1,44 @@
+import std/unittest
+import pkg/constantine/ethereum_bls_signatures
+import codexvalidator/signatures
+import ./examples
+
+suite "Signature scheme":
+
+  test "uses BLS private key as validator identity":
+    check signatures.Identity is ethereum_bls_signatures.SecretKey
+
+  test "uses BLS public key as validator identifier":
+    check signatures.Identifier is ethereum_bls_signatures.PublicKey
+
+  test "uses BLS signatures":
+    check signatures.Signature is ethereum_bls_signatures.Signature
+
+  test "can create a new random identity":
+    var identity1, identity2: Identity
+    Identity.random(identity1)
+    Identity.random(identity2)
+    check identity1.identifier != identity2.identifier
+
+  test "derives identifier (public key) from the identity (private key)":
+    var identity: Identity
+    Identity.random(identity)
+    var publicKey: PublicKey
+    derive_pubkey(publicKey, identity)
+    check identity.identifier == publicKey
+
+  test "identity can sign messages":
+    var identity: Identity
+    Identity.random(identity)
+    let message = seq[byte].example
+    let signature1, signature2 = identity.sign(message)
+    check signature1 == signature2
+
+  test "signatures can be verified":
+    var identity1, identity2: Identity
+    Identity.random(identity1)
+    Identity.random(identity2)
+    let message = seq[byte].example
+    let signature = identity1.sign(message)
+    check signature.verify(identity1.identifier, message)
+    check not signature.verify(identity2.identifier, message)
diff --git a/tests/tests.nim b/tests/tests.nim
index aeebbae..f64b2dd 100644
--- a/tests/tests.nim
+++ b/tests/tests.nim
@@ -1,3 +1,4 @@
+import ./codexvalidator/testSignatures
 import ./codexvalidator/testTransaction
 
 {.warning[UnusedImport]:off.}