Add EncodedNodeId (#601)

Adds the EncodedNodeId interface that can be either a public key or a pair channel id, direction that's more compact.
This is used as introduction node for blinded routes.
We also use EncodedNodeId for the next node to relay a message to. Which is not in the spec yet but is necessary for us since we have no way to resolve the compact node id to a public key ourselves. It requires a compatible peer that accepts this format.

src/commonMain/kotlin/fr/acinq/lightning/EncodedNodeId.kt

@@ -0,0 +1,22 @@
+package fr.acinq.lightning
+
+import fr.acinq.bitcoin.PublicKey
+import fr.acinq.bitcoin.io.Input
+import fr.acinq.bitcoin.io.Output
+import fr.acinq.lightning.wire.LightningCodecs
+
+sealed class EncodedNodeId {
+    /** Nodes are usually identified by their public key. */
+    data class Plain(val publicKey: PublicKey) : EncodedNodeId() {
+        override fun toString(): String = publicKey.toString()
+    }
+
+    /** For compactness, nodes may be identified by the shortChannelId of one of their public channels. */
+    data class ShortChannelIdDir(val isNode1: Boolean, val scid: ShortChannelId) : EncodedNodeId() {
+        override fun toString(): String = if (isNode1) "<-$scid" else "$scid->"
+    }
+
+    companion object {
+        operator fun invoke(publicKey: PublicKey): EncodedNodeId = Plain(publicKey)
+    }
+}

src/commonMain/kotlin/fr/acinq/lightning/crypto/RouteBlinding.kt

@@ -4,20 +4,21 @@ import fr.acinq.bitcoin.ByteVector
 import fr.acinq.bitcoin.Crypto
 import fr.acinq.bitcoin.PrivateKey
 import fr.acinq.bitcoin.PublicKey
+import fr.acinq.lightning.EncodedNodeId
 import fr.acinq.lightning.crypto.sphinx.Sphinx
 
 object RouteBlinding {
 
     /**
-     * @param publicKey            introduction node's public key (which cannot be blinded since the sender need to find a route to it).
+     * @param nodeId               introduction node's id (which cannot be blinded since the sender need to find a route to it).
      * @param blindedPublicKey     blinded public key, which hides the real public key.
      * @param blindingEphemeralKey blinding tweak that can be used by the receiving node to derive the private key that
      *                             matches the blinded public key.
      * @param encryptedPayload     encrypted payload that can be decrypted with the introduction node's private key and the
      *                             blinding ephemeral key.
      */
     data class IntroductionNode(
-        val publicKey: PublicKey,
+        val nodeId: EncodedNodeId,
         val blindedPublicKey: PublicKey,
         val blindingEphemeralKey: PublicKey,
         val encryptedPayload: ByteVector
@@ -37,7 +38,7 @@ object RouteBlinding {
      * @param blindedNodes       blinded nodes (including the introduction node).
      */
     data class BlindedRoute(
-        val introductionNodeId: PublicKey,
+        val introductionNodeId: EncodedNodeId,
         val blindingKey: PublicKey,
         val blindedNodes: List<BlindedNode>
     ) {
@@ -78,7 +79,7 @@ object RouteBlinding {
             e *= PrivateKey(Crypto.sha256(blindingKey.value.toByteArray() + sharedSecret.toByteArray()))
             Pair(BlindedNode(blindedPublicKey, ByteVector(encryptedPayload + mac)), blindingKey)
         }.unzip()
-        return BlindedRoute(publicKeys.first(), blindingKeys.first(), blindedHops)
+        return BlindedRoute(EncodedNodeId(publicKeys.first()), blindingKeys.first(), blindedHops)
     }
 
     /**

src/commonMain/kotlin/fr/acinq/lightning/wire/LightningCodecs.kt

@@ -1,13 +1,12 @@
 package fr.acinq.lightning.wire
 
-import fr.acinq.bitcoin.ByteVector
-import fr.acinq.bitcoin.ByteVector32
-import fr.acinq.bitcoin.TxHash
-import fr.acinq.bitcoin.TxId
+import fr.acinq.bitcoin.*
 import fr.acinq.bitcoin.crypto.Pack
 import fr.acinq.bitcoin.io.ByteArrayOutput
 import fr.acinq.bitcoin.io.Input
 import fr.acinq.bitcoin.io.Output
+import fr.acinq.lightning.EncodedNodeId
+import fr.acinq.lightning.ShortChannelId
 import fr.acinq.lightning.utils.leftPaddedCopyOf
 import kotlin.jvm.JvmStatic
 
@@ -225,4 +224,26 @@ object LightningCodecs {
         return bytes(input, length)
     }
 
+    fun encodedNodeId(input: Input): EncodedNodeId {
+        val firstByte = byte(input)
+        if (firstByte == 0 || firstByte == 1) {
+            val isNode1 = firstByte == 0
+            val scid = ShortChannelId(int64(input))
+            return EncodedNodeId.ShortChannelIdDir(isNode1, scid)
+        } else if (firstByte == 2 || firstByte == 3) {
+            val publicKey = PublicKey(ByteArray(1) { firstByte.toByte() } + bytes(input, 32))
+            return EncodedNodeId.Plain(publicKey)
+        } else {
+            throw IllegalArgumentException("unexpected first byte: $firstByte")
+        }
+    }
+
+    fun writeEncodedNodeId(input: EncodedNodeId, out: Output): Unit = when (input) {
+        is EncodedNodeId.Plain -> writeBytes(input.publicKey.value, out)
+        is EncodedNodeId.ShortChannelIdDir -> {
+            writeByte(if (input.isNode1) 0 else 1, out)
+            writeInt64(input.scid.toLong(), out)
+        }
+    }
+
 }

src/commonMain/kotlin/fr/acinq/lightning/wire/MessageOnion.kt

@@ -6,9 +6,9 @@ import fr.acinq.bitcoin.io.ByteArrayInput
 import fr.acinq.bitcoin.io.ByteArrayOutput
 import fr.acinq.bitcoin.io.Input
 import fr.acinq.bitcoin.io.Output
+import fr.acinq.lightning.EncodedNodeId
 import fr.acinq.lightning.crypto.RouteBlinding
 
-
 sealed class OnionMessagePayloadTlv : Tlv {
     /**
      * Onion messages may provide a reply path, allowing the recipient to send a message back to the original sender.
@@ -17,8 +17,9 @@ sealed class OnionMessagePayloadTlv : Tlv {
     data class ReplyPath(val blindedRoute: RouteBlinding.BlindedRoute) : OnionMessagePayloadTlv() {
         override val tag: Long get() = ReplyPath.tag
         override fun write(out: Output) {
-            LightningCodecs.writeBytes(blindedRoute.introductionNodeId.value, out)
+            LightningCodecs.writeEncodedNodeId(blindedRoute.introductionNodeId, out)
             LightningCodecs.writeBytes(blindedRoute.blindingKey.value, out)
+            LightningCodecs.writeByte(blindedRoute.blindedNodes.size, out)
             for (hop in blindedRoute.blindedNodes) {
                 LightningCodecs.writeBytes(hop.blindedPublicKey.value, out)
                 LightningCodecs.writeU16(hop.encryptedPayload.size(), out)
@@ -29,15 +30,14 @@ sealed class OnionMessagePayloadTlv : Tlv {
         companion object : TlvValueReader<ReplyPath> {
             const val tag: Long = 2
             override fun read(input: Input): ReplyPath {
-                val firstNodeId = PublicKey(LightningCodecs.bytes(input, 33))
+                val firstNodeId = LightningCodecs.encodedNodeId(input)
                 val blinding = PublicKey(LightningCodecs.bytes(input, 33))
-                val path = sequence {
-                    while (input.availableBytes > 0) {
-                        val blindedPublicKey = PublicKey(LightningCodecs.bytes(input, 33))
-                        val encryptedPayload = ByteVector(LightningCodecs.bytes(input, LightningCodecs.u16(input)))
-                        yield(RouteBlinding.BlindedNode(blindedPublicKey, encryptedPayload))
-                    }
-                }.toList()
+                val numHops = LightningCodecs.byte(input)
+                val path = (0 until numHops).map {
+                    val blindedPublicKey = PublicKey(LightningCodecs.bytes(input, 33))
+                    val encryptedPayload = ByteVector(LightningCodecs.bytes(input, LightningCodecs.u16(input)))
+                    RouteBlinding.BlindedNode(blindedPublicKey, encryptedPayload)
+                }
                 return ReplyPath(RouteBlinding.BlindedRoute(firstNodeId, blinding, path))
             }
         }

src/commonMain/kotlin/fr/acinq/lightning/wire/RouteBlinding.kt

@@ -6,6 +6,7 @@ import fr.acinq.bitcoin.io.ByteArrayInput
 import fr.acinq.bitcoin.io.ByteArrayOutput
 import fr.acinq.bitcoin.io.Input
 import fr.acinq.bitcoin.io.Output
+import fr.acinq.lightning.EncodedNodeId
 
 
 sealed class RouteBlindingEncryptedDataTlv : Tlv {
@@ -22,14 +23,14 @@ sealed class RouteBlindingEncryptedDataTlv : Tlv {
     }
 
     /** Id of the next node. */
-    data class OutgoingNodeId(val nodeId: PublicKey) : RouteBlindingEncryptedDataTlv() {
+    data class OutgoingNodeId(val nodeId: EncodedNodeId) : RouteBlindingEncryptedDataTlv() {
         override val tag: Long get() = OutgoingNodeId.tag
-        override fun write(out: Output) = LightningCodecs.writeBytes(nodeId.value, out)
+        override fun write(out: Output) = LightningCodecs.writeEncodedNodeId(nodeId, out)
 
         companion object : TlvValueReader<OutgoingNodeId> {
             const val tag: Long = 4
             override fun read(input: Input): OutgoingNodeId =
-                OutgoingNodeId(PublicKey(LightningCodecs.bytes(input, 33)))
+                OutgoingNodeId(LightningCodecs.encodedNodeId(input))
         }
     }
 

src/commonTest/kotlin/fr/acinq/lightning/crypto/sphinx/SphinxTestsCommon.kt

@@ -4,6 +4,7 @@ import fr.acinq.bitcoin.ByteVector
 import fr.acinq.bitcoin.ByteVector32
 import fr.acinq.bitcoin.PrivateKey
 import fr.acinq.bitcoin.PublicKey
+import fr.acinq.lightning.EncodedNodeId
 import fr.acinq.lightning.crypto.RouteBlinding
 import fr.acinq.lightning.crypto.sphinx.Sphinx.computeEphemeralPublicKeysAndSharedSecrets
 import fr.acinq.lightning.crypto.sphinx.Sphinx.decodePayloadLength
@@ -562,8 +563,8 @@ class SphinxTestsCommon : LightningTestSuite() {
     fun `create blinded route -- reference test vector`() {
         val sessionKey = PrivateKey(ByteVector32("0101010101010101010101010101010101010101010101010101010101010101"))
         val blindedRoute = RouteBlinding.create(sessionKey, publicKeys, routeBlindingPayloads)
-        assertEquals(blindedRoute.introductionNode.publicKey, publicKeys[0])
-        assertEquals(blindedRoute.introductionNodeId, publicKeys[0])
+        assertEquals(blindedRoute.introductionNode.nodeId, EncodedNodeId(publicKeys[0]))
+        assertEquals(blindedRoute.introductionNodeId, EncodedNodeId(publicKeys[0]))
         assertEquals(blindedRoute.introductionNode.blindedPublicKey, PublicKey.fromHex("02ec68ed555f5d18b12fe0e2208563c3566032967cf11dc29b20c345449f9a50a2"))
         assertEquals(blindedRoute.introductionNode.blindingEphemeralKey, PublicKey.fromHex("031b84c5567b126440995d3ed5aaba0565d71e1834604819ff9c17f5e9d5dd078f"))
         assertEquals(blindedRoute.introductionNode.encryptedPayload, ByteVector("af4fbf67bd52520bdfab6a88cd4e7f22ffad08d8b153b17ff303f93fdb4712"))
@@ -641,7 +642,7 @@ class SphinxTestsCommon : LightningTestSuite() {
             )
             Pair(RouteBlinding.create(sessionKey, publicKeys.take(2), payloads), payloads)
         }
-        val blindedRoute = RouteBlinding.BlindedRoute(publicKeys[0], blindedRouteStart.blindingKey, blindedRouteStart.blindedNodes + blindedRouteEnd.blindedNodes)
+        val blindedRoute = RouteBlinding.BlindedRoute(EncodedNodeId(publicKeys[0]), blindedRouteStart.blindingKey, blindedRouteStart.blindedNodes + blindedRouteEnd.blindedNodes)
         assertEquals(blindedRoute.blindingKey, PublicKey.fromHex("024d4b6cd1361032ca9bd2aeb9d900aa4d45d9ead80ac9423374c451a7254d0766"))
         assertEquals(blindedRoute.blindedNodeIds, listOf(
             PublicKey.fromHex("0303176d13958a8a59d59517a6223e12cf291ba5f65c8011efcdca0a52c3850abc"),

src/commonTest/kotlin/fr/acinq/lightning/wire/LightningCodecsTestsCommon.kt

@@ -818,4 +818,26 @@ class LightningCodecsTestsCommon : LightningTestSuite() {
         }
 
     }
+
+    @Test
+    fun `encoded node id`() {
+        val testCases = mapOf(
+            ByteVector.fromHex("00 0d950b0001c80000") to
+                    EncodedNodeId.ShortChannelIdDir(isNode1 = true, ShortChannelId(890123, 456, 0)),
+            ByteVector.fromHex("01 0c0a14000d800005") to
+                    EncodedNodeId.ShortChannelIdDir(isNode1 = false, ShortChannelId(789012, 3456, 5)),
+            ByteVector.fromHex("022d3b15cea00ee4a8e710b082bef18f0f3409cc4e7aff41c26eb0a4d3ab20dd73") to
+                    EncodedNodeId.Plain(PublicKey.fromHex("022d3b15cea00ee4a8e710b082bef18f0f3409cc4e7aff41c26eb0a4d3ab20dd73")),
+            ByteVector.fromHex("03ba3c458e3299eb19d2e07ae86453f4290bcdf8689707f0862f35194397c45922") to
+                    EncodedNodeId.Plain(PublicKey.fromHex("03ba3c458e3299eb19d2e07ae86453f4290bcdf8689707f0862f35194397c45922")),
+        )
+
+        for (testCase in testCases) {
+            val (encoded, decoded) = testCase
+            val out = ByteArrayOutput()
+            LightningCodecs.writeEncodedNodeId(decoded, out)
+            assertEquals(encoded, out.toByteArray().toByteVector())
+            assertEquals(decoded, LightningCodecs.encodedNodeId(ByteArrayInput(encoded.toByteArray())))
+        }
+    }
 }

src/commonTest/kotlin/fr/acinq/lightning/wire/RouteBlindingTestsCommon.kt

@@ -2,6 +2,7 @@ package fr.acinq.lightning.wire
 
 import fr.acinq.bitcoin.ByteVector
 import fr.acinq.bitcoin.PublicKey
+import fr.acinq.lightning.EncodedNodeId
 import fr.acinq.lightning.tests.utils.LightningTestSuite
 import fr.acinq.lightning.wire.RouteBlindingEncryptedDataTlv.*
 import kotlin.test.Test
@@ -14,7 +15,7 @@ class RouteBlindingTestsCommon : LightningTestSuite() {
             ByteVector("01080000000000000000 042102edabbd16b41c8371b92ef2f04c1185b4f03b6dcd52ba9b78d9d7c89c8f221145") to RouteBlindingEncryptedData(
                 TlvStream(
                     Padding(ByteVector("0000000000000000")),
-                    OutgoingNodeId(PublicKey(ByteVector("02edabbd16b41c8371b92ef2f04c1185b4f03b6dcd52ba9b78d9d7c89c8f221145")))
+                    OutgoingNodeId(EncodedNodeId(PublicKey(ByteVector("02edabbd16b41c8371b92ef2f04c1185b4f03b6dcd52ba9b78d9d7c89c8f221145"))))
                 )
             ),
             ByteVector("0109000000000000000000 06204242424242424242424242424242424242424242424242424242424242424242") to RouteBlindingEncryptedData(
@@ -24,10 +25,10 @@ class RouteBlindingTestsCommon : LightningTestSuite() {
                 )
             ),
             ByteVector("0421032c0b7cf95324a07d05398b240174dc0c2be444d96b159aa6c7f7b1e668680991") to RouteBlindingEncryptedData(
-                TlvStream(OutgoingNodeId(PublicKey(ByteVector("032c0b7cf95324a07d05398b240174dc0c2be444d96b159aa6c7f7b1e668680991"))))
+                TlvStream(OutgoingNodeId(EncodedNodeId(PublicKey(ByteVector("032c0b7cf95324a07d05398b240174dc0c2be444d96b159aa6c7f7b1e668680991")))))
             ),
             ByteVector("042102edabbd16b41c8371b92ef2f04c1185b4f03b6dcd52ba9b78d9d7c89c8f221145") to RouteBlindingEncryptedData(
-                TlvStream(OutgoingNodeId(PublicKey(ByteVector("02edabbd16b41c8371b92ef2f04c1185b4f03b6dcd52ba9b78d9d7c89c8f221145"))))
+                TlvStream(OutgoingNodeId(EncodedNodeId(PublicKey(ByteVector("02edabbd16b41c8371b92ef2f04c1185b4f03b6dcd52ba9b78d9d7c89c8f221145")))))
             ),
             ByteVector("010f000000000000000000000000000000 061000112233445566778899aabbccddeeff") to RouteBlindingEncryptedData(
                 TlvStream(
@@ -38,12 +39,12 @@ class RouteBlindingTestsCommon : LightningTestSuite() {
             ByteVector("0121000000000000000000000000000000000000000000000000000000000000000000 04210324653eac434488002cc06bbfb7f10fe18991e35f9fe4302dbea6d2353dc0ab1c") to RouteBlindingEncryptedData(
                 TlvStream(
                     Padding(ByteVector("000000000000000000000000000000000000000000000000000000000000000000")),
-                    OutgoingNodeId(PublicKey(ByteVector("0324653eac434488002cc06bbfb7f10fe18991e35f9fe4302dbea6d2353dc0ab1c")))
+                    OutgoingNodeId(EncodedNodeId(PublicKey(ByteVector("0324653eac434488002cc06bbfb7f10fe18991e35f9fe4302dbea6d2353dc0ab1c"))))
                 )
             ),
             ByteVector("0421027f31ebc5462c1fdce1b737ecff52d37d75dea43ce11c74d25aa297165faa2007 0821031b84c5567b126440995d3ed5aaba0565d71e1834604819ff9c17f5e9d5dd078f") to RouteBlindingEncryptedData(
                 TlvStream(
-                    OutgoingNodeId(PublicKey(ByteVector("027f31ebc5462c1fdce1b737ecff52d37d75dea43ce11c74d25aa297165faa2007"))),
+                    OutgoingNodeId(EncodedNodeId(PublicKey(ByteVector("027f31ebc5462c1fdce1b737ecff52d37d75dea43ce11c74d25aa297165faa2007")))),
                     NextBlinding(PublicKey(ByteVector("031b84c5567b126440995d3ed5aaba0565d71e1834604819ff9c17f5e9d5dd078f")))
                 )
             ),