| | | 1 | | using NBitcoin; |
| | | 2 | | |
| | | 3 | | namespace NLightning.Infrastructure.Protocol.Models; |
| | | 4 | | |
| | | 5 | | using Crypto.Hashes; |
| | | 6 | | |
| | | 7 | | /// <summary> |
| | | 8 | | /// Manages Lightning Network commitment numbers and their obscuring as defined in BOLT3. |
| | | 9 | | /// </summary> |
| | | 10 | | public sealed class CommitmentNumber |
| | | 11 | | { |
| | | 12 | | /// <summary> |
| | | 13 | | /// Gets the commitment number value. |
| | | 14 | | /// </summary> |
| | 556 | 15 | | public ulong Value { get; private set; } |
| | | 16 | | |
| | | 17 | | /// <summary> |
| | | 18 | | /// Gets the obscuring factor derived from payment basepoints. |
| | | 19 | | /// </summary> |
| | 296 | 20 | | public ulong ObscuringFactor { get; } |
| | | 21 | | |
| | | 22 | | /// <summary> |
| | | 23 | | /// Gets the obscured commitment number (value XOR obscuring factor). |
| | | 24 | | /// </summary> |
| | 288 | 25 | | public ulong ObscuredValue => Value ^ ObscuringFactor; |
| | | 26 | | |
| | | 27 | | /// <summary> |
| | | 28 | | /// Represents a commitment number in the Lightning Network. |
| | | 29 | | /// </summary> |
| | 252 | 30 | | public CommitmentNumber(PubKey localPaymentBasepoint, PubKey remotePaymentBasepoint, |
| | 252 | 31 | | ulong initialValue = 0) |
| | | 32 | | { |
| | 252 | 33 | | ArgumentNullException.ThrowIfNull(localPaymentBasepoint); |
| | 252 | 34 | | ArgumentNullException.ThrowIfNull(remotePaymentBasepoint); |
| | | 35 | | |
| | 252 | 36 | | Value = initialValue; |
| | 252 | 37 | | ObscuringFactor = CalculateObscuringFactor(localPaymentBasepoint, remotePaymentBasepoint); |
| | 252 | 38 | | } |
| | | 39 | | |
| | | 40 | | /// <summary> |
| | | 41 | | /// Increments the commitment number. |
| | | 42 | | /// </summary> |
| | | 43 | | /// <returns>This instance for chaining.</returns> |
| | | 44 | | public CommitmentNumber Increment() |
| | | 45 | | { |
| | 4 | 46 | | Value++; |
| | 4 | 47 | | return this; |
| | | 48 | | } |
| | | 49 | | |
| | | 50 | | /// <summary> |
| | | 51 | | /// Calculates the transaction locktime value using the obscured commitment number. |
| | | 52 | | /// </summary> |
| | | 53 | | /// <returns>The transaction locktime.</returns> |
| | | 54 | | public LockTime CalculateLockTime() |
| | | 55 | | { |
| | 140 | 56 | | return new LockTime((0x20 << 24) | (uint)(ObscuredValue & 0xFFFFFF)); |
| | | 57 | | } |
| | | 58 | | |
| | | 59 | | /// <summary> |
| | | 60 | | /// Calculates the transaction sequence value using the obscured commitment number. |
| | | 61 | | /// </summary> |
| | | 62 | | /// <returns>The transaction sequence.</returns> |
| | | 63 | | public Sequence CalculateSequence() |
| | | 64 | | { |
| | 144 | 65 | | return new Sequence((uint)((0x80UL << 24) | ((ObscuredValue >> 24) & 0xFFFFFF))); |
| | | 66 | | } |
| | | 67 | | |
| | | 68 | | /// <summary> |
| | | 69 | | /// Calculates the 48-bit obscuring factor by hashing the concatenation of payment basepoints. |
| | | 70 | | /// </summary> |
| | | 71 | | /// <param name="localBasepoint">The local payment basepoint.</param> |
| | | 72 | | /// <param name="remoteBasepoint">The remote payment basepoint.</param> |
| | | 73 | | /// <returns>The 48-bit obscuring factor as ulong.</returns> |
| | | 74 | | private static ulong CalculateObscuringFactor(PubKey localBasepoint, PubKey remoteBasepoint) |
| | | 75 | | { |
| | 252 | 76 | | using var sha256 = new Sha256(); |
| | | 77 | | |
| | | 78 | | // Hash the concatenation of payment basepoints |
| | 252 | 79 | | sha256.AppendData(localBasepoint.ToBytes()); |
| | 252 | 80 | | sha256.AppendData(remoteBasepoint.ToBytes()); |
| | | 81 | | |
| | 252 | 82 | | Span<byte> hashResult = stackalloc byte[32]; |
| | 252 | 83 | | sha256.GetHashAndReset(hashResult); |
| | | 84 | | |
| | | 85 | | // Extract the lower 48 bits (6 bytes) of the hash |
| | 252 | 86 | | ulong obscuringFactor = 0; |
| | 3528 | 87 | | for (var i = 26; i < 32; i++) // Last 6 bytes of the 32-byte hash |
| | | 88 | | { |
| | 1512 | 89 | | obscuringFactor = (obscuringFactor << 8) | hashResult[i]; |
| | | 90 | | } |
| | | 91 | | |
| | 252 | 92 | | return obscuringFactor; |
| | 252 | 93 | | } |
| | | 94 | | } |