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Make XEdDSASigning work with firmware generated signatures #131

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661db93
Private Ed25519 key derivation based on firmware's XEdDSA::priv_curve…
lkosson Jul 6, 2026
3c4b753
Removed double hashing to stay in line with firmware's implementation
lkosson Jul 6, 2026
77b44b2
Removed unused code
lkosson Jul 6, 2026
9d39e89
Removed useShortHash references
lkosson Jul 6, 2026
bdd3ade
Added test cases for signatures produced by 2.8 firmware
lkosson Jul 8, 2026
a69d61b
Helper for verifying MeshPacket signature
lkosson Jul 8, 2026
eea93b5
Helper for adding MeshPacket signature
lkosson Jul 8, 2026
b74e3f9
Force positive sign on Ed25519 key derived from X25519
lkosson Jul 8, 2026
869330b
Added docs
lkosson Jul 8, 2026
ded4b1b
Test case for Ed25519 public key derived from private key matched the…
lkosson Jul 8, 2026
fbfbf28
Test both positive and negative (scalar sign-flipping) GenerateEdDSAK…
lkosson Jul 8, 2026
10286f5
Proper derivation of public Ed25519 key from private key
lkosson Jul 8, 2026
403d184
Reduce scalar before negating
lkosson Jul 8, 2026
f3f475d
Deterministic test cases for positive/negative scalar sign during pub…
lkosson Jul 8, 2026
1cc60e1
Use Ed25519 Sign/Verify primitives directly
lkosson Jul 8, 2026
28cbbcb
Sign method, as expected by the firmware
lkosson Jul 9, 2026
812b0f6
Internal BouncyCastle's methods imported only once
lkosson Jul 9, 2026
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70 changes: 53 additions & 17 deletions Meshtastic.Test/Crypto/XEdDSASigningTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -50,6 +50,26 @@ public void ConvertX25519PublicKeyToEd25519_Should_ProduceValidEdPublicKey()
Assert.That(edPublicKey[31] & 0x80, Is.EqualTo(0)); // Sign bit should be 0
}

[Test]
public void ConvertX25519PublicKeyToEd25519_Should_EqualToGenerateEdDSAKeysFromX25519_Positive()
{
var x25519PrivateKey = Convert.FromBase64String("+ATTWKM68dlArUzWrXWlQm45Gi3ZYrOdDt2z5VT5+2o=");
var x25519PublicKey = PKIEncryption.GetPublicKeyFromPrivateKey(x25519PrivateKey);
var edPublicKeyFromPublic = XEdDSASigning.ConvertX25519PublicKeyToEd25519(x25519PublicKey);
var (_, edPublicKeyFromPrivate) = XEdDSASigning.GenerateEdDSAKeysFromX25519(x25519PrivateKey);
Assert.That(edPublicKeyFromPrivate, Is.EqualTo(edPublicKeyFromPublic));
}

[Test]
public void ConvertX25519PublicKeyToEd25519_Should_EqualToGenerateEdDSAKeysFromX25519_Negative()
{
var x25519PrivateKey = Convert.FromBase64String("wJNheemu5n2oPgpu0BpEdomsPlChBSM8gAO7RRWkT2w=");
var x25519PublicKey = PKIEncryption.GetPublicKeyFromPrivateKey(x25519PrivateKey);
var edPublicKeyFromPublic = XEdDSASigning.ConvertX25519PublicKeyToEd25519(x25519PublicKey);
var (_, edPublicKeyFromPrivate) = XEdDSASigning.GenerateEdDSAKeysFromX25519(x25519PrivateKey);
Assert.That(edPublicKeyFromPrivate, Is.EqualTo(edPublicKeyFromPublic));
}

[Test]
public void Sign_Should_ProduceValidSignature()
{
Expand All @@ -58,7 +78,7 @@ public void Sign_Should_ProduceValidSignature()
var (edPrivateKey, edPublicKey) = XEdDSASigning.GenerateEdDSAKeysFromX25519(_testPrivateKey);

// Act
var signature = XEdDSASigning.Sign(message, edPrivateKey, edPublicKey, useShortHash: true);
var signature = XEdDSASigning.Sign(message, edPrivateKey, edPublicKey);

// Assert
Assert.That(signature, Is.Not.Null);
Expand All @@ -72,10 +92,10 @@ public void Verify_Should_ReturnTrue_ForValidSignature()
// Arrange
var message = Encoding.UTF8.GetBytes("Test message for verification");
var (edPrivateKey, edPublicKey) = XEdDSASigning.GenerateEdDSAKeysFromX25519(_testPrivateKey);
var signature = XEdDSASigning.Sign(message, edPrivateKey, edPublicKey, useShortHash: true);
var signature = XEdDSASigning.Sign(message, edPrivateKey, edPublicKey);

// Act
var isValid = XEdDSASigning.Verify(message, signature, edPublicKey, useShortHash: true);
var isValid = XEdDSASigning.Verify(message, signature, edPublicKey);

// Assert
Assert.That(isValid, Is.True);
Expand All @@ -90,7 +110,7 @@ public void Verify_Should_ReturnFalse_ForInvalidSignature()
var (_, edPublicKey) = XEdDSASigning.GenerateEdDSAKeysFromX25519(_testPrivateKey);

// Act
var isValid = XEdDSASigning.Verify(message, invalidSignature, edPublicKey, useShortHash: true);
var isValid = XEdDSASigning.Verify(message, invalidSignature, edPublicKey);

// Assert
Assert.That(isValid, Is.False);
Expand All @@ -103,29 +123,45 @@ public void Verify_Should_ReturnFalse_ForTamperedMessage()
var originalMessage = Encoding.UTF8.GetBytes("Original message");
var tamperedMessage = Encoding.UTF8.GetBytes("Tampered message");
var (edPrivateKey, edPublicKey) = XEdDSASigning.GenerateEdDSAKeysFromX25519(_testPrivateKey);
var signature = XEdDSASigning.Sign(originalMessage, edPrivateKey, edPublicKey, useShortHash: true);
var signature = XEdDSASigning.Sign(originalMessage, edPrivateKey, edPublicKey);

// Act
var isValid = XEdDSASigning.Verify(tamperedMessage, signature, edPublicKey, useShortHash: true);
var isValid = XEdDSASigning.Verify(tamperedMessage, signature, edPublicKey);

// Assert
Assert.That(isValid, Is.False);
}

[TestCase(true)]
[TestCase(false)]
public void SignAndVerify_Should_Work_WithBothHashTypes(bool useShortHash)
[Test]
public void Verify_RealLife_ValidSignature()
{
// Arrange
var message = Encoding.UTF8.GetBytes("Test message for both hash types");
var (edPrivateKey, edPublicKey) = XEdDSASigning.GenerateEdDSAKeysFromX25519(_testPrivateKey);
var rawCapturedPacket = Convert.FromBase64String("DbVdZX4V/////xgVIkwIARIEVGVzdEgBUkDdbuxwz2lvDyBKpCW1ojj+pMPfnRfWiUsDwf1cwisx+82L7fA5/g5OW5LrpWfU4z73AHqysNLKBUOt3TfhBEQONXE20CI9ieBNakgHWGR4B5gBtQE=");
var senderPublicKey = Convert.FromBase64String("t0hKwMywRb2nKFOvVXcjFAGPWgCSta4ZwEkgPkgJWwM=");
var meshPacket = MeshPacket.Parser.ParseFrom(rawCapturedPacket);
var isValid = XEdDSASigning.VerifyPacketSignature(senderPublicKey, meshPacket);
Assert.That(isValid, Is.True);
}

// Act
var signature = XEdDSASigning.Sign(message, edPrivateKey, edPublicKey, useShortHash);
var isValid = XEdDSASigning.Verify(message, signature, edPublicKey, useShortHash);
[Test]
public void Verify_RealLife_InvalidPubkey()
{
var rawCapturedPacket = Convert.FromBase64String("DbVdZX4V/////xgVIkwIARIEVGVzdEgBUkDdbuxwz2lvDyBKpCW1ojj+pMPfnRfWiUsDwf1cwisx+82L7fA5/g5OW5LrpWfU4z73AHqysNLKBUOt3TfhBEQONXE20CI9ieBNakgHWGR4B5gBtQE=");
var senderPublicKey = Convert.FromBase64String("t0hKwMywRb2nKFOvVXcjFAGPWgCSta4ZwEkgPkgJWwM=");
senderPublicKey[0]++;
var meshPacket = MeshPacket.Parser.ParseFrom(rawCapturedPacket);
var isValid = XEdDSASigning.VerifyPacketSignature(senderPublicKey, meshPacket);
Assert.That(isValid, Is.False);
}

// Assert
Assert.That(isValid, Is.True);
[Test]
public void Verify_RealLife_TamperedMessage()
{
var rawCapturedPacket = Convert.FromBase64String("DbVdZX4V/////xgVIkwIARIEVGVzdEgBUkDdbuxwz2lvDyBKpCW1ojj+pMPfnRfWiUsDwf1cwisx+82L7fA5/g5OW5LrpWfU4z73AHqysNLKBUOt3TfhBEQONXE20CI9ieBNakgHWGR4B5gBtQE=");
var senderPublicKey = Convert.FromBase64String("t0hKwMywRb2nKFOvVXcjFAGPWgCSta4ZwEkgPkgJWwM=");
var meshPacket = MeshPacket.Parser.ParseFrom(rawCapturedPacket);
meshPacket.Decoded.Payload = Google.Protobuf.ByteString.CopyFromUtf8("Tampered");
var isValid = XEdDSASigning.VerifyPacketSignature(senderPublicKey, meshPacket);
Assert.That(isValid, Is.False);
}

[Test]
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