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BLS aggregate signatures #7669

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merged 3 commits into from
Oct 28, 2024
Merged

BLS aggregate signatures #7669

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7f6c76c
implement bls aggregate signatures
Marchhill Oct 28, 2024
b39e2c1
rename param
Marchhill Oct 28, 2024
e40cdd4
add link to bls rfc
Marchhill Oct 28, 2024
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40 changes: 40 additions & 0 deletions src/Nethermind/Nethermind.Core.Test/Crypto/BlsSignerTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,7 @@ public class BlsTests
{
private static readonly byte[] SkBytes = [0x2c, 0xd4, 0xba, 0x40, 0x6b, 0x52, 0x24, 0x59, 0xd5, 0x7a, 0x0b, 0xed, 0x51, 0xa3, 0x97, 0x43, 0x5c, 0x0b, 0xb1, 0x1d, 0xd5, 0xf3, 0xca, 0x11, 0x52, 0xb3, 0x69, 0x4b, 0xb9, 0x1d, 0x7c, 0x22];
private static readonly byte[] MsgBytes = [0x3e, 0x00, 0xef, 0x2f, 0x89, 0x5f, 0x40, 0xd6, 0x7f, 0x5b, 0xb8, 0xe8, 0x1f, 0x09, 0xa5, 0xa1, 0x2c, 0x84, 0x0e, 0xc3, 0xce, 0x9a, 0x7f, 0x3b, 0x18, 0x1b, 0xe1, 0x88, 0xef, 0x71, 0x1a, 0x1e];
private static int AggregateSignerCount = 100;

[Test]
public void Calculate_signature()
Expand All @@ -34,6 +35,18 @@ public void Verify_signature()
Assert.That(BlsSigner.Verify(publicKey.ToAffine(), s, MsgBytes));
}

[Test]
public void Verify_aggregate_signature()
{
Span<byte> skBytes = new byte[AggregateSignerCount * 32];
Span<byte> publicKeys = new byte[AggregateSignerCount * BlsSigner.PkCompressedSz];

GenerateKeys(skBytes, publicKeys);

BlsSigner.Signature s = BlsSigner.SignAggregate(skBytes, MsgBytes);
Assert.That(BlsSigner.VerifyAggregate(publicKeys, s, MsgBytes));
}

[Test]
public void Rejects_bad_signature()
{
Expand All @@ -49,6 +62,18 @@ public void Rejects_bad_signature()
Assert.That(BlsSigner.Verify(publicKey.ToAffine(), bad, MsgBytes), Is.False);
}

[Test]
public void Rejects_missing_aggregate_signature()
{
Span<byte> skBytes = new byte[AggregateSignerCount * 32];
Span<byte> publicKeys = new byte[AggregateSignerCount * BlsSigner.PkCompressedSz];

GenerateKeys(skBytes, publicKeys);

BlsSigner.Signature s = BlsSigner.SignAggregate(skBytes[32..], MsgBytes);
Assert.That(BlsSigner.VerifyAggregate(publicKeys, s, MsgBytes), Is.False);
}

[Test]
public void Public_key_from_private_key()
{
Expand All @@ -59,4 +84,19 @@ public void Public_key_from_private_key()

Assert.That(publicKey.Compress(), Is.EqualTo(expected));
}

private void GenerateKeys(Span<byte> skBytes, Span<byte> publicKeyBytes)
{
Bls.SecretKey masterSk = new(SkBytes, Bls.ByteOrder.LittleEndian);
for (int i = 0; i < AggregateSignerCount; i++)
{
int offset = i * 32;
Bls.SecretKey sk = new(masterSk, (uint)i);
sk.ToBendian().CopyTo(skBytes[offset..(offset + 32)]);

G1 publicKey = new();
publicKey.FromSk(sk);
publicKey.Compress().CopyTo(publicKeyBytes[(i * BlsSigner.PkCompressedSz)..]);
}
}
}
48 changes: 48 additions & 0 deletions src/Nethermind/Nethermind.Crypto/BlsSigner.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -8,13 +8,17 @@

namespace Nethermind.Crypto;

// https://www.ietf.org/archive/id/draft-irtf-cfrg-bls-signature-05.html

using G1 = Bls.P1;
using G1Affine = Bls.P1Affine;
using G2 = Bls.P2;
using G2Affine = Bls.P2Affine;
using GT = Bls.PT;

public static class BlsSigner
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{
public const int PkCompressedSz = 384 / 8;
private static readonly byte[] Cryptosuite = Encoding.UTF8.GetBytes("BLS_SIG_BLS12381G2_XMD:SHA-256_SSWU_RO_POP_");
private const int InputLength = 64;

Expand All @@ -27,6 +31,29 @@ public static Signature Sign(Bls.SecretKey sk, ReadOnlySpan<byte> message)
return new(p.Compress());
}

[SkipLocalsInit]
public static Signature SignAggregate(ReadOnlySpan<byte> skBytes, ReadOnlySpan<byte> message)
{
if (skBytes.Length % 32 != 0)
{
throw new Bls.BlsException(Bls.ERROR.WRONGSIZE);
}

G2 p = new(stackalloc long[G2.Sz]);
G2 agg = new(stackalloc long[G2.Sz]);
agg.Zero();

for (int i = 0; i < skBytes.Length; i += 32)
{
Bls.SecretKey sk = new(skBytes.Slice(i, 32));
p.HashTo(message, Cryptosuite);
p.SignWith(sk);
agg.Aggregate(p.ToAffine());
}

return new(agg.Compress());
}

[SkipLocalsInit]
public static bool Verify(G1Affine publicKey, Signature signature, ReadOnlySpan<byte> message)
{
Expand All @@ -53,6 +80,27 @@ public static bool Verify(G1Affine publicKey, Signature signature, ReadOnlySpan<
}
}

[SkipLocalsInit]
public static bool VerifyAggregate(ReadOnlySpan<byte> publicKeyBytes, Signature signature, ReadOnlySpan<byte> message)
{
if (publicKeyBytes.Length % PkCompressedSz != 0)
{
throw new Bls.BlsException(Bls.ERROR.WRONGSIZE);
}

G1Affine pk = new(stackalloc long[G1Affine.Sz]);
G1 agg = new(stackalloc long[G1.Sz]);
agg.Zero();

for (int i = 0; i < publicKeyBytes.Length; i += PkCompressedSz)
{
pk.Decode(publicKeyBytes.Slice(i, PkCompressedSz));
agg.Aggregate(pk);
}

return Verify(agg.ToAffine(), signature, message);
}

// Compressed G2 point
public readonly ref struct Signature()
{
Expand Down