wire+chaincfg: add signet params

This commit adds all necessary chain parameters for connecting to the
public signet network.
Reference: https://github.com/bitcoin/bitcoin/pull/18267

chaincfg/genesis.go

@@ -170,3 +170,31 @@ var simNetGenesisBlock = wire.MsgBlock{
 	},
 	Transactions: []*wire.MsgTx{&genesisCoinbaseTx},
 }
+
+// sigNetGenesisHash is the hash of the first block in the block chain for the
+// signet test network.
+var sigNetGenesisHash = chainhash.Hash{
+	0xf6, 0x1e, 0xee, 0x3b, 0x63, 0xa3, 0x80, 0xa4,
+	0x77, 0xa0, 0x63, 0xaf, 0x32, 0xb2, 0xbb, 0xc9,
+	0x7c, 0x9f, 0xf9, 0xf0, 0x1f, 0x2c, 0x42, 0x25,
+	0xe9, 0x73, 0x98, 0x81, 0x08, 0x00, 0x00, 0x00,
+}
+
+// sigNetGenesisMerkleRoot is the hash of the first transaction in the genesis
+// block for the signet test network. It is the same as the merkle root for
+// the main network.
+var sigNetGenesisMerkleRoot = genesisMerkleRoot
+
+// sigNetGenesisBlock defines the genesis block of the block chain which serves
+// as the public transaction ledger for the signet test network.
+var sigNetGenesisBlock = wire.MsgBlock{
+	Header: wire.BlockHeader{
+		Version:    1,
+		PrevBlock:  chainhash.Hash{},         // 0000000000000000000000000000000000000000000000000000000000000000
+		MerkleRoot: sigNetGenesisMerkleRoot,  // 4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b
+		Timestamp:  time.Unix(1598918400, 0), // 2020-09-01 00:00:00 +0000 UTC
+		Bits:       0x1e0377ae,               // 503543726 [00000377ae000000000000000000000000000000000000000000000000000000]
+		Nonce:      52613770,
+	},
+	Transactions: []*wire.MsgTx{&genesisCoinbaseTx},
+}

chaincfg/genesis_test.go

@@ -118,6 +118,33 @@ func TestSimNetGenesisBlock(t *testing.T) {
 	}
 }
 
+// TestSigNetGenesisBlock tests the genesis block of the signet test network for
+// validity by checking the encoded bytes and hashes.
+func TestSigNetGenesisBlock(t *testing.T) {
+	// Encode the genesis block to raw bytes.
+	var buf bytes.Buffer
+	err := SigNetParams.GenesisBlock.Serialize(&buf)
+	if err != nil {
+		t.Fatalf("TestSigNetGenesisBlock: %v", err)
+	}
+
+	// Ensure the encoded block matches the expected bytes.
+	if !bytes.Equal(buf.Bytes(), sigNetGenesisBlockBytes) {
+		t.Fatalf("TestSigNetGenesisBlock: Genesis block does not "+
+			"appear valid - got %v, want %v",
+			spew.Sdump(buf.Bytes()),
+			spew.Sdump(sigNetGenesisBlockBytes))
+	}
+
+	// Check hash of the block against expected hash.
+	hash := SigNetParams.GenesisBlock.BlockHash()
+	if !SigNetParams.GenesisHash.IsEqual(&hash) {
+		t.Fatalf("TestSigNetGenesisBlock: Genesis block hash does "+
+			"not appear valid - got %v, want %v", spew.Sdump(hash),
+			spew.Sdump(SigNetParams.GenesisHash))
+	}
+}
+
 // genesisBlockBytes are the wire encoded bytes for the genesis block of the
 // main network as of protocol version 60002.
 var genesisBlockBytes = []byte{
@@ -281,3 +308,44 @@ var simNetGenesisBlockBytes = []byte{
 	0x8a, 0x4c, 0x70, 0x2b, 0x6b, 0xf1, 0x1d, 0x5f, /* |.Lp+k.._|*/
 	0xac, 0x00, 0x00, 0x00, 0x00, /* |.....|    */
 }
+
+// sigNetGenesisBlockBytes are the wire encoded bytes for the genesis block of
+// the signet test network as of protocol version 70002.
+var sigNetGenesisBlockBytes = []byte{
+	0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* |...@....| */
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* |........| */
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* |........| */
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* |........| */
+	0x00, 0x00, 0x00, 0x00, 0x3b, 0xa3, 0xed, 0xfd, /* |........| */
+	0x7a, 0x7b, 0x12, 0xb2, 0x7a, 0xc7, 0x2c, 0x3e, /* |....;...| */
+	0x67, 0x76, 0x8f, 0x61, 0x7f, 0xc8, 0x1b, 0xc3, /* |z{..z.,>| */
+	0x88, 0x8a, 0x51, 0x32, 0x3a, 0x9f, 0xb8, 0xaa, /* |gv.a....| */
+	0x4b, 0x1e, 0x5e, 0x4a, 0x00, 0x8f, 0x4d, 0x5f, /* |..Q2:...| */
+	0xae, 0x77, 0x03, 0x1e, 0x8a, 0xd2, 0x22, 0x03, /* |K.^J..M_| */
+	0x01, 0x01, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, /* |.w....".| */
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* |........| */
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* |........| */
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* |........| */
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xff, 0xff, /* |........| */
+	0xff, 0xff, 0x4d, 0x04, 0xff, 0xff, 0x00, 0x1d, /* |........| */
+	0x01, 0x04, 0x45, 0x54, 0x68, 0x65, 0x20, 0x54, /* |..M.....| */
+	0x69, 0x6d, 0x65, 0x73, 0x20, 0x30, 0x33, 0x2f, /* |..EThe T| */
+	0x4a, 0x61, 0x6e, 0x2f, 0x32, 0x30, 0x30, 0x39, /* |imes 03/| */
+	0x20, 0x43, 0x68, 0x61, 0x6e, 0x63, 0x65, 0x6c, /* |Jan/2009| */
+	0x6c, 0x6f, 0x72, 0x20, 0x6f, 0x6e, 0x20, 0x62, /* | Chancel| */
+	0x72, 0x69, 0x6e, 0x6b, 0x20, 0x6f, 0x66, 0x20, /* |lor on b| */
+	0x73, 0x65, 0x63, 0x6f, 0x6e, 0x64, 0x20, 0x62, /* |rink of| */
+	0x61, 0x69, 0x6c, 0x6f, 0x75, 0x74, 0x20, 0x66, /* |second b| */
+	0x6f, 0x72, 0x20, 0x62, 0x61, 0x6e, 0x6b, 0x73, /* |ailout f| */
+	0xff, 0xff, 0xff, 0xff, 0x01, 0x00, 0xf2, 0x05, /* |or banks| */
+	0x2a, 0x01, 0x00, 0x00, 0x00, 0x43, 0x41, 0x04, /* |........| */
+	0x67, 0x8a, 0xfd, 0xb0, 0xfe, 0x55, 0x48, 0x27, /* |*....CA.| */
+	0x19, 0x67, 0xf1, 0xa6, 0x71, 0x30, 0xb7, 0x10, /* |g....UH'| */
+	0x5c, 0xd6, 0xa8, 0x28, 0xe0, 0x39, 0x09, 0xa6, /* |.g..q0..| */
+	0x79, 0x62, 0xe0, 0xea, 0x1f, 0x61, 0xde, 0xb6, /* |\..(.9..| */
+	0x49, 0xf6, 0xbc, 0x3f, 0x4c, 0xef, 0x38, 0xc4, /* |yb...a..| */
+	0xf3, 0x55, 0x04, 0xe5, 0x1e, 0xc1, 0x12, 0xde, /* |I..?L.8.| */
+	0x5c, 0x38, 0x4d, 0xf7, 0xba, 0x0b, 0x8d, 0x57, /* |.U......| */
+	0x8a, 0x4c, 0x70, 0x2b, 0x6b, 0xf1, 0x1d, 0x5f, /* |\8M....W| */
+	0xac, 0x00, 0x00, 0x00, 0x00, /* |.....| */
+}

chaincfg/params.go

@@ -5,6 +5,8 @@
 package chaincfg
 
 import (
+	"encoding/binary"
+	"encoding/hex"
 	"errors"
 	"math"
 	"math/big"
@@ -38,6 +40,30 @@ var (
 	// simNetPowLimit is the highest proof of work value a Bitcoin block
 	// can have for the simulation test network.  It is the value 2^255 - 1.
 	simNetPowLimit = new(big.Int).Sub(new(big.Int).Lsh(bigOne, 255), bigOne)
+
+	// sigNetPowLimit is the highest proof of work value a bitcoin block can
+	// have for the signet test network. It is the value 0x0377ae << 216.
+	sigNetPowLimit = new(big.Int).Lsh(new(big.Int).SetInt64(0x0377ae), 216)
+
+	// DefaultSignetChallenge is the byte representation of the signet
+	// challenge for the default (public, Taproot enabled) signet network.
+	// This is the binary equivalent of the bitcoin script
+	//  1 03ad5e0edad18cb1f0fc0d28a3d4f1f3e445640337489abb10404f2d1e086be430
+	//  0359ef5021964fe22d6f8e05b2463c9540ce96883fe3b278760f048f5189f2e6c4 2
+	//  OP_CHECKMULTISIG
+	DefaultSignetChallenge, _ = hex.DecodeString(
+		"512103ad5e0edad18cb1f0fc0d28a3d4f1f3e445640337489abb10404f2d" +
+			"1e086be430210359ef5021964fe22d6f8e05b2463c9540ce9688" +
+			"3fe3b278760f048f5189f2e6c452ae",
+	)
+
+	// DefaultSignetDNSSeeds is the list of seed nodes for the default
+	// (public, Taproot enabled) signet network.
+	DefaultSignetDNSSeeds = []DNSSeed{
+		{"178.128.221.177", false},
+		{"2a01:7c8:d005:390::5", false},
+		{"v7ajjeirttkbnt32wpy3c6w3emwnfr3fkla7hpxcfokr3ysd3kqtzmqd.onion:38333", false},
+	}
 )
 
 // Checkpoint identifies a known good point in the block chain.  Using
@@ -96,6 +122,11 @@ const (
 	// includes the deployment of BIPS 141, 142, 144, 145, 147 and 173.
 	DeploymentSegwit
 
+	// DeploymentTaproot defines the rule change deployment ID for the
+	// Taproot (+Schnorr) soft-fork package. The taproot package includes
+	// the deployment of BIPS 340, 341 and 342.
+	DeploymentTaproot
+
 	// NOTE: DefinedDeployments must always come last since it is used to
 	// determine how many defined deployments there currently are.
 
@@ -578,6 +609,107 @@ var SimNetParams = Params{
 	HDCoinType: 115, // ASCII for s
 }
 
+// SigNetParams defines the network parameters for the default public signet
+// Bitcoin network. Not to be confused with the regression test network, this
+// network is sometimes simply called "signet" or "taproot signet".
+var SigNetParams = CustomSignetParams(
+	DefaultSignetChallenge, DefaultSignetDNSSeeds,
+)
+
+// CustomSignetParams creates network parameters for a custom signet network
+// from a challenge. The challenge is the binary compiled version of the block
+// challenge script.
+func CustomSignetParams(challenge []byte, dnsSeeds []DNSSeed) Params {
+	// The message start is defined as the first four bytes of the sha256d
+	// of the challenge script, as a single push (i.e. prefixed with the
+	// challenge script length).
+	challengeLength := byte(len(challenge))
+	hashDouble := chainhash.DoubleHashB(
+		append([]byte{challengeLength}, challenge...),
+	)
+
+	// We use little endian encoding of the hash prefix to be in line with
+	// the other wire network identities.
+	net := binary.LittleEndian.Uint32(hashDouble[0:4])
+	return Params{
+		Name:        "signet",
+		Net:         wire.BitcoinNet(net),
+		DefaultPort: "38333",
+		DNSSeeds:    dnsSeeds,
+
+		// Chain parameters
+		GenesisBlock:             &sigNetGenesisBlock,
+		GenesisHash:              &sigNetGenesisHash,
+		PowLimit:                 sigNetPowLimit,
+		PowLimitBits:             0x1e0377ae,
+		BIP0034Height:            1,
+		BIP0065Height:            1,
+		BIP0066Height:            1,
+		CoinbaseMaturity:         100,
+		SubsidyReductionInterval: 210000,
+		TargetTimespan:           time.Hour * 24 * 14, // 14 days
+		TargetTimePerBlock:       time.Minute * 10,    // 10 minutes
+		RetargetAdjustmentFactor: 4,                   // 25% less, 400% more
+		ReduceMinDifficulty:      false,
+		MinDiffReductionTime:     time.Minute * 20, // TargetTimePerBlock * 2
+		GenerateSupported:        false,
+
+		// Checkpoints ordered from oldest to newest.
+		Checkpoints: nil,
+
+		// Consensus rule change deployments.
+		//
+		// The miner confirmation window is defined as:
+		//   target proof of work timespan / target proof of work spacing
+		RuleChangeActivationThreshold: 1916, // 95% of 2016
+		MinerConfirmationWindow:       2016,
+		Deployments: [DefinedDeployments]ConsensusDeployment{
+			DeploymentTestDummy: {
+				BitNumber:  28,
+				StartTime:  1199145601, // January 1, 2008 UTC
+				ExpireTime: 1230767999, // December 31, 2008 UTC
+			},
+			DeploymentCSV: {
+				BitNumber:  0,
+				StartTime:  0,             // Always available for vote
+				ExpireTime: math.MaxInt64, // Never expires
+			},
+			DeploymentSegwit: {
+				BitNumber:  1,
+				StartTime:  0,             // Always available for vote
+				ExpireTime: math.MaxInt64, // Never expires.
+			},
+			DeploymentTaproot: {
+				BitNumber:  2,
+				StartTime:  0,             // Always available for vote
+				ExpireTime: math.MaxInt64, // Never expires.
+			},
+		},
+
+		// Mempool parameters
+		RelayNonStdTxs: false,
+
+		// Human-readable part for Bech32 encoded segwit addresses, as defined in
+		// BIP 173.
+		Bech32HRPSegwit: "tb", // always tb for test net
+
+		// Address encoding magics
+		PubKeyHashAddrID:        0x6f, // starts with m or n
+		ScriptHashAddrID:        0xc4, // starts with 2
+		WitnessPubKeyHashAddrID: 0x03, // starts with QW
+		WitnessScriptHashAddrID: 0x28, // starts with T7n
+		PrivateKeyID:            0xef, // starts with 9 (uncompressed) or c (compressed)
+
+		// BIP32 hierarchical deterministic extended key magics
+		HDPrivateKeyID: [4]byte{0x04, 0x35, 0x83, 0x94}, // starts with tprv
+		HDPublicKeyID:  [4]byte{0x04, 0x35, 0x87, 0xcf}, // starts with tpub
+
+		// BIP44 coin type used in the hierarchical deterministic path for
+		// address generation.
+		HDCoinType: 1,
+	}
+}
+
 var (
 	// ErrDuplicateNet describes an error where the parameters for a Bitcoin
 	// network could not be set due to the network already being a standard

chaincfg/params_test.go

@@ -6,6 +6,8 @@ package chaincfg
 
 import (
 	"bytes"
+	"encoding/hex"
+	"math/big"
 	"testing"
 )
 
@@ -84,3 +86,50 @@ func TestInvalidHDKeyID(t *testing.T) {
 		t.Fatalf("HDPrivateKeyToPublicKeyID: want err ErrUnknownHDKeyID, got %v", err)
 	}
 }
+
+func TestSigNetPowLimit(t *testing.T) {
+	sigNetPowLimitHex, _ := hex.DecodeString(
+		"00000377ae000000000000000000000000000000000000000000000000000000",
+	)
+	powLimit := new(big.Int).SetBytes(sigNetPowLimitHex)
+	if sigNetPowLimit.Cmp(powLimit) != 0 {
+		t.Fatalf("Signet PoW limit bits (%s) not equal to big int (%s)",
+			sigNetPowLimit.Text(16), powLimit.Text(16))
+	}
+
+	if compactToBig(sigNetGenesisBlock.Header.Bits).Cmp(powLimit) != 0 {
+		t.Fatalf("Signet PoW limit header bits (%d) not equal to big "+
+			"int (%s)", sigNetGenesisBlock.Header.Bits,
+			powLimit.Text(16))
+	}
+}
+
+// compactToBig is a copy of the blockchain.CompactToBig function. We copy it
+// here so we don't run into a circular dependency just because of a test.
+func compactToBig(compact uint32) *big.Int {
+	// Extract the mantissa, sign bit, and exponent.
+	mantissa := compact & 0x007fffff
+	isNegative := compact&0x00800000 != 0
+	exponent := uint(compact >> 24)
+
+	// Since the base for the exponent is 256, the exponent can be treated
+	// as the number of bytes to represent the full 256-bit number.  So,
+	// treat the exponent as the number of bytes and shift the mantissa
+	// right or left accordingly.  This is equivalent to:
+	// N = mantissa * 256^(exponent-3)
+	var bn *big.Int
+	if exponent <= 3 {
+		mantissa >>= 8 * (3 - exponent)
+		bn = big.NewInt(int64(mantissa))
+	} else {
+		bn = big.NewInt(int64(mantissa))
+		bn.Lsh(bn, 8*(exponent-3))
+	}
+
+	// Make it negative if the sign bit is set.
+	if isNegative {
+		bn = bn.Neg(bn)
+	}
+
+	return bn
+}