Signet implementation

contrib/example.conf

@@ -0,0 +1,16 @@
+
+chain=signet
+
+[signet]
+con_genesis_style=signet_old
+signet_blockscript=512103e464a9f3070da4d3e0b34ce971ff36f3e07c47a8f4beadf32e8ea7e2afa8a82451ae
+signet_siglen=77
+# DG seed node
+seednode=178.128.221.177
+bech32_hrp=sb
+pchmessagestart=F0C7706A
+pubkeyprefix=125
+scriptprefix=87
+secretprefix=217
+extpubkeyprefix=043587CF
+extprvkeyprefix=04358394

contrib/signet/issuer/issuer.sh

@@ -0,0 +1,75 @@
+#!/usr/bin/env bash
+# Copyright (c) 2018 The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+export LC_ALL=C
+
+#
+# Issue blocks using a local node at a given interval.
+#
+
+if [ $# -lt 3 ]; then
+    echo "syntax: $0 <min_time> <max_time> <bitcoin-cli path> [<bitcoin-cli args>]" ; exit 1
+fi
+
+function log()
+{
+    echo "- $(date +%H:%M:%S): $*"
+}
+
+min_time=$1
+shift
+max_time=$1
+shift
+bcli=$1
+shift
+
+# https://stackoverflow.com/questions/806906/how-do-i-test-if-a-variable-is-a-number-in-bash
+re='^[0-9]+$'
+if ! [[ $min_time =~ $re ]] ; then
+   echo "error: min_time $min_time is not a number" ; exit 1
+fi
+if ! [[ $max_time =~ $re ]] ; then
+   echo "error: max_time $max_time is not a number" ; exit 1
+fi
+
+let randinterval=max_time-min_time
+if [ $randinterval -lt 1 ]; then
+    echo "error: interval min..max must be positive and greater than 0" ; exit 1
+fi
+
+if ! [ -e "$bcli" ]; then
+    which "$bcli" &> /dev/null
+    if [ $? -ne 0 ]; then
+        echo "error: unable to find bitcoin binary: $bcli" ; exit 1
+    fi
+fi
+
+echo "- checking node status"
+conns=$($bcli "$@" getconnectioncount)
+
+if [ $? -ne 0 ]; then
+    echo "node error" ; exit 1
+fi
+
+if [ $conns -lt 1 ]; then
+    echo "warning: node is not connected to any other node"
+fi
+
+log "node OK with $conns connection(s)"
+log "mining in random intervals between $min_time .. $max_time seconds"
+log "hit ^C to stop"
+
+while true; do
+    let rv=$RANDOM%$randinterval
+    echo -n -e "- $(date +%H:%M:%S): next block in $rv seconds..."
+    sleep $rv
+    echo -n -e " [submit]"
+    blockhash=$($bcli "$@" getnewblockhex true)
+    if [ $? -ne 0 ]; then
+        echo "node error; aborting" ; exit 1
+    fi
+    echo ""
+    log "broadcasting block $($bcli "$@" getblockcount) $blockhash to $($bcli "$@" getconnectioncount) peer(s)"
+done

src/chain.h

@@ -405,6 +405,16 @@ public:
         READWRITE(nTime);
         READWRITE(nBits);
         READWRITE(nNonce);
+        if (g_solution_blocks && !(s.GetType() & SER_GETHASH)) {
+            uint256 hash = GetBlockHash();
+            READWRITE(g_blockheader_payload_map[hash]);
+            size_t len = GetSizeOfCompactSize(g_blockheader_payload_map[hash].size()) + g_blockheader_payload_map[hash].size();
+            while (len < g_solution_block_len) {
+                uint8_t padding = 0;
+                READWRITE(padding);
+                len++;
+            }
+        }
     }
 
     uint256 GetBlockHash() const

src/chainparams.cpp

@@ -428,6 +428,10 @@ class CCustomParams : public CRegTestParams {
         consensus.nMinimumChainWork = uint256S(args.GetArg("-con_nminimumchainwork", "0x0"));
         consensus.defaultAssumeValid = uint256S(args.GetArg("-con_defaultassumevalid", "0x00"));
 
+        consensus.blockscript = ParseHex(args.GetArg("-signet_blockscript", ""));
+        g_solution_blocks = !consensus.blockscript.empty();
+        g_solution_block_len = consensus.siglen = args.GetArg("-signet_siglen", 77);
+
         nPruneAfterHeight = (uint64_t)args.GetArg("-npruneafterheight", nPruneAfterHeight);
         fDefaultConsistencyChecks = args.GetBoolArg("-fdefaultconsistencychecks", fDefaultConsistencyChecks);
         fMineBlocksOnDemand = args.GetBoolArg("-fmineblocksondemand", fMineBlocksOnDemand);
@@ -464,15 +468,29 @@ class CCustomParams : public CRegTestParams {
     {
         if (consensus.genesis_style == "regtest2_style") {
             // Same style as in https://github.com/bitcoin/bitcoin/pull/8994
+            assert(consensus.blockscript.empty() && "consensus.blockscript is for signets");
             genesis = CreateGenesisBlock(strNetworkID.c_str(), CScript(OP_TRUE), 1296688602, 2, 0x207fffff, 1, 50 * COIN);
 
         } else if (consensus.genesis_style == "default_style") {
             CHashWriter h(SER_DISK, 0);
             h << strNetworkID;
+            if (!consensus.blockscript.empty()) {
+                h << consensus.blockscript << consensus.siglen;
+            }
             uint256 hash = h.GetHash();
             CScript coinbase_sig = CScript() << std::vector<uint8_t>(hash.begin(), hash.end());
             genesis = CreateGenesisBlock(coinbase_sig, CScript(OP_TRUE), 1296688602, 2, 0x207fffff, 1, 50 * COIN);
 
+        } else if (consensus.genesis_style == "signet_old") {
+            // Same style as in https://github.com/kallewoof/bitcoin/pull/5
+            assert(!consensus.blockscript.empty() && "Signets require consensus.blockscript");
+            CHashWriter h(SER_DISK, 0);
+            h << consensus.blockscript << consensus.siglen;
+            uint256 hash = h.GetHash();
+            CScript coinbase_sig = CScript() << std::vector<uint8_t>(hash.begin(), hash.end());
+            CScript genesis_out = CScript() << OP_RETURN;
+            genesis = CreateGenesisBlock(coinbase_sig, genesis_out, 1534313275, 0, 0x1d00ffff, 1, 50 * COIN);
+
         } else {
             throw std::runtime_error(strprintf("%s: Unknown consensus.genesis_style %s.", __func__, consensus.genesis_style));
         }

src/chainparamsbase.cpp

@@ -21,9 +21,11 @@ void SetupChainParamsBaseOptions()
     gArgs.AddArg("-regtest", "Enter regression test mode, which uses a special chain in which blocks can be solved instantly. "
                                    "This is intended for regression testing tools and app development.", true, OptionsCategory::CHAINPARAMS);
     gArgs.AddArg("-testnet", "Use the test chain", false, OptionsCategory::CHAINPARAMS);
-    gArgs.AddArg("-con_genesis_style=<style>", "Use genesis style <style> (default: default_style). Allowed values: default_style, regtest2_style", true, OptionsCategory::CHAINPARAMS);
+    gArgs.AddArg("-con_genesis_style=<style>", "Use genesis style <style> (default: default_style). Allowed values: default_style, regtest2_style, signet_old", true, OptionsCategory::CHAINPARAMS);
     gArgs.AddArg("-vbparams=deployment:start:end", "Use given start/end times for specified version bits deployment (regtest or custom only)", true, OptionsCategory::CHAINPARAMS);
     gArgs.AddArg("-seednode=<ip>", "Use specified node as seed node. This option can be specified multiple times to connect to multiple nodes. (custom only)", true, OptionsCategory::CHAINPARAMS);
+    gArgs.AddArg("-signet_blockscript", "Blocks must satisfy the given script to be considered valid instead of using pow. If empty, and by default, it is ignored. (custom only)", true, OptionsCategory::CHAINPARAMS);
+    gArgs.AddArg("-signet_siglen", "The length of the signature must be exactly this long (padded to this length, if shorter). All block headers in this network are of length 80 + this value (custom only)", true, OptionsCategory::CHAINPARAMS);
 }
 
 static std::unique_ptr<CBaseChainParams> globalChainBaseParams;

src/consensus/params.h

@@ -76,7 +76,11 @@ struct Params {
     int64_t DifficultyAdjustmentInterval() const { return nPowTargetTimespan / nPowTargetSpacing; }
     uint256 nMinimumChainWork;
     uint256 defaultAssumeValid;
+
+    std::vector<uint8_t> blockscript;
+    uint32_t siglen;
 };
+
 } // namespace Consensus
 
 #endif // BITCOIN_CONSENSUS_PARAMS_H

src/miner.cpp

@@ -55,6 +55,9 @@ int64_t UpdateTime(CBlockHeader* pblock, const Consensus::Params& consensusParam
 BlockAssembler::Options::Options() {
     blockMinFeeRate = CFeeRate(DEFAULT_BLOCK_MIN_TX_FEE);
     nBlockMaxWeight = DEFAULT_BLOCK_MAX_WEIGHT;
+
+    // Make room for the signature in the block header, if this is a signet block
+    if (g_solution_blocks) nBlockMaxWeight -= g_solution_block_len;
 }
 
 BlockAssembler::BlockAssembler(const CChainParams& params, const Options& options) : chainparams(params)

src/policy/policy.cpp

@@ -14,6 +14,7 @@
 #include <util.h>
 #include <utilstrencodings.h>
 
+unsigned int GetStandardScriptVerifyFlags() { return STANDARD_SCRIPT_VERIFY_FLAGS; }
 
 CAmount GetDustThreshold(const CTxOut& txout, const CFeeRate& dustRelayFeeIn)
 {

src/policy/policy.h

@@ -68,6 +68,8 @@ static constexpr unsigned int STANDARD_SCRIPT_VERIFY_FLAGS = MANDATORY_SCRIPT_VE
                                                              SCRIPT_VERIFY_WITNESS_PUBKEYTYPE |
                                                              SCRIPT_VERIFY_CONST_SCRIPTCODE;
 
+unsigned int GetStandardScriptVerifyFlags();
+
 /** For convenience, standard but not mandatory verify flags. */
 static constexpr unsigned int STANDARD_NOT_MANDATORY_VERIFY_FLAGS = STANDARD_SCRIPT_VERIFY_FLAGS & ~MANDATORY_SCRIPT_VERIFY_FLAGS;
 

src/pow.cpp

@@ -9,6 +9,9 @@
 #include <chain.h>
 #include <primitives/block.h>
 #include <uint256.h>
+#include <script/interpreter.h>
+
+unsigned int GetStandardScriptVerifyFlags();
 
 unsigned int GetNextWorkRequired(const CBlockIndex* pindexLast, const CBlockHeader *pblock, const Consensus::Params& params)
 {
@@ -71,8 +74,17 @@ unsigned int CalculateNextWorkRequired(const CBlockIndex* pindexLast, int64_t nF
     return bnNew.GetCompact();
 }
 
-bool CheckProofOfWork(uint256 hash, unsigned int nBits, const Consensus::Params& params)
+bool CheckProofOfWork(const uint256& hash, unsigned int nBits, const Consensus::Params& params)
 {
+    if (g_solution_blocks) {
+        if (hash == params.hashGenesisBlock) return true;
+        SimpleSignatureChecker bsc(hash);
+        const auto& payload = g_blockheader_payload_map.at(hash);
+        CScript solution = CScript(payload.begin(), payload.end());
+        CScript challenge = CScript(params.blockscript.begin(), params.blockscript.end());
+        return VerifyScript(solution, challenge, nullptr, GetStandardScriptVerifyFlags(), bsc);
+    }
+
     bool fNegative;
     bool fOverflow;
     arith_uint256 bnTarget;

src/pow.h

@@ -18,6 +18,6 @@ unsigned int GetNextWorkRequired(const CBlockIndex* pindexLast, const CBlockHead
 unsigned int CalculateNextWorkRequired(const CBlockIndex* pindexLast, int64_t nFirstBlockTime, const Consensus::Params&);
 
 /** Check whether a block hash satisfies the proof-of-work requirement specified by nBits */
-bool CheckProofOfWork(uint256 hash, unsigned int nBits, const Consensus::Params&);
+bool CheckProofOfWork(const uint256& hash, unsigned int nBits, const Consensus::Params&);
 
 #endif // BITCOIN_POW_H

src/primitives/block.cpp

@@ -10,6 +10,10 @@
 #include <utilstrencodings.h>
 #include <crypto/common.h>
 
+bool g_solution_blocks = false;
+size_t g_solution_block_len = 0;
+std::map<uint256,std::vector<uint8_t>> g_blockheader_payload_map;
+
 uint256 CBlockHeader::GetHash() const
 {
     return SerializeHash(*this);

src/primitives/block.h

@@ -10,6 +10,23 @@
 #include <serialize.h>
 #include <uint256.h>
 
+/**
+ * If true, block headers contain a payload equal to a Bitcoin Script solution
+ * to a signet challenge as defined in the chain params.
+ */
+extern bool g_solution_blocks;
+/**
+ * If non-zero, defines an enforced size requirement for block header payloads.
+ * It requires that all blocks are of size 80 + (this value) bytes.
+ */
+extern size_t g_solution_block_len;
+
+/**
+ * Contains a mapping of hash to signature data for each block header
+ * in signet networks.
+ */
+extern std::map<uint256,std::vector<uint8_t>> g_blockheader_payload_map;
+
 /** Nodes collect new transactions into a block, hash them into a hash tree,
  * and scan through nonce values to make the block's hash satisfy proof-of-work
  * requirements.  When they solve the proof-of-work, they broadcast the block
@@ -43,6 +60,15 @@ public:
         READWRITE(nTime);
         READWRITE(nBits);
         READWRITE(nNonce);
+        if (g_solution_blocks && !(s.GetType() & SER_GETHASH)) {
+            READWRITE(g_blockheader_payload_map[GetHash()]);
+            size_t len = GetSizeOfCompactSize(g_blockheader_payload_map[GetHash()].size()) + g_blockheader_payload_map[GetHash()].size();
+            while (len < g_solution_block_len) {
+                uint8_t padding = 0;
+                READWRITE(padding);
+                len++;
+            }
+        }
     }
 
     void SetNull()

src/rpc/blockchain.cpp

@@ -115,16 +115,16 @@ UniValue blockToJSON(const CBlock& block, const CBlockIndex* blockindex, bool tx
 {
     AssertLockHeld(cs_main);
     UniValue result(UniValue::VOBJ);
-    result.pushKV("hash", blockindex->GetBlockHash().GetHex());
+    result.pushKV("hash", block.GetHash().GetHex());
     int confirmations = -1;
     // Only report confirmations if the block is on the main chain
-    if (chainActive.Contains(blockindex))
+    if (blockindex && chainActive.Contains(blockindex))
         confirmations = chainActive.Height() - blockindex->nHeight + 1;
     result.pushKV("confirmations", confirmations);
     result.pushKV("strippedsize", (int)::GetSerializeSize(block, SER_NETWORK, PROTOCOL_VERSION | SERIALIZE_TRANSACTION_NO_WITNESS));
     result.pushKV("size", (int)::GetSerializeSize(block, SER_NETWORK, PROTOCOL_VERSION));
     result.pushKV("weight", (int)::GetBlockWeight(block));
-    result.pushKV("height", blockindex->nHeight);
+    if (blockindex) result.pushKV("height", blockindex->nHeight);
     result.pushKV("version", block.nVersion);
     result.pushKV("versionHex", strprintf("%08x", block.nVersion));
     result.pushKV("merkleroot", block.hashMerkleRoot.GetHex());
@@ -142,18 +142,23 @@ UniValue blockToJSON(const CBlock& block, const CBlockIndex* blockindex, bool tx
     }
     result.pushKV("tx", txs);
     result.pushKV("time", block.GetBlockTime());
-    result.pushKV("mediantime", (int64_t)blockindex->GetMedianTimePast());
+    if (blockindex) result.pushKV("mediantime", (int64_t)blockindex->GetMedianTimePast());
     result.pushKV("nonce", (uint64_t)block.nNonce);
     result.pushKV("bits", strprintf("%08x", block.nBits));
-    result.pushKV("difficulty", GetDifficulty(blockindex));
-    result.pushKV("chainwork", blockindex->nChainWork.GetHex());
-    result.pushKV("nTx", (uint64_t)blockindex->nTx);
+    if (blockindex) result.pushKV("difficulty", GetDifficulty(blockindex));
+    if (blockindex) result.pushKV("chainwork", blockindex->nChainWork.GetHex());
+    if (blockindex) result.pushKV("nTx", (uint64_t)blockindex->nTx);
 
-    if (blockindex->pprev)
+    if (blockindex && blockindex->pprev)
         result.pushKV("previousblockhash", blockindex->pprev->GetBlockHash().GetHex());
-    CBlockIndex *pnext = chainActive.Next(blockindex);
-    if (pnext)
-        result.pushKV("nextblockhash", pnext->GetBlockHash().GetHex());
+    if (blockindex) {
+        CBlockIndex *pnext = chainActive.Next(blockindex);
+        if (pnext)
+            result.pushKV("nextblockhash", pnext->GetBlockHash().GetHex());
+    }
+    if (g_solution_blocks && g_blockheader_payload_map.count(block.GetHash())) {
+        result.pushKV("signet-solution", HexStr(g_blockheader_payload_map.at(block.GetHash())));
+    }
     return result;
 }
 

src/rpc/client.cpp

@@ -55,6 +55,7 @@ static const CRPCConvertParam vRPCConvertParams[] =
     { "getbalance", 1, "minconf" },
     { "getbalance", 2, "include_watchonly" },
     { "getblockhash", 0, "height" },
+    { "getnewblockhex", 0, "broadcast" },
     { "waitforblockheight", 0, "height" },
     { "waitforblockheight", 1, "timeout" },
     { "waitforblock", 1, "timeout" },

src/rpc/mining.cpp

@@ -695,7 +695,7 @@ protected:
     }
 };
 
-static UniValue submitblock(const JSONRPCRequest& request)
+UniValue submitblock(const JSONRPCRequest& request)
 {
     // We allow 2 arguments for compliance with BIP22. Argument 2 is ignored.
     if (request.fHelp || request.params.size() < 1 || request.params.size() > 2) {
@@ -725,6 +725,11 @@ static UniValue submitblock(const JSONRPCRequest& request)
     }
 
     uint256 hash = block.GetHash();
+
+    if (!request.params[1].isNull()) {
+        g_blockheader_payload_map[hash] = ParseHex(request.params[1].get_str());
+    }
+
     {
         LOCK(cs_main);
         const CBlockIndex* pindex = LookupBlockIndex(hash);
@@ -942,7 +947,6 @@ static const CRPCCommand commands[] =
     { "mining",             "getblocktemplate",       &getblocktemplate,       {"template_request"} },
     { "mining",             "submitblock",            &submitblock,            {"hexdata","dummy"} },
 
-
     { "generating",         "generatetoaddress",      &generatetoaddress,      {"nblocks","address","maxtries"} },
 
     { "hidden",             "estimatefee",            &estimatefee,            {} },

src/script/interpreter.cpp

@@ -1416,6 +1416,22 @@ bool GenericTransactionSignatureChecker<T>::CheckSequence(const CScriptNum& nSeq
 template class GenericTransactionSignatureChecker<CTransaction>;
 template class GenericTransactionSignatureChecker<CMutableTransaction>;
 
+bool SimpleSignatureChecker::CheckSig(const std::vector<unsigned char>& vchSigIn, const std::vector<unsigned char>& vchPubKey, const CScript& scriptCode, SigVersion sigversion) const
+{
+    CPubKey pubkey(vchPubKey);
+    if (!pubkey.IsValid())
+        return false;
+
+    // Hash type is one byte tacked on to the end of the signature
+    std::vector<unsigned char> vchSig(vchSigIn);
+    if (vchSig.empty())
+        return false;
+    // int nHashType = vchSig.back();
+    vchSig.pop_back();
+
+    return pubkey.Verify(hash, vchSig);
+}
+
 static bool VerifyWitnessProgram(const CScriptWitness& witness, int witversion, const std::vector<unsigned char>& program, unsigned int flags, const BaseSignatureChecker& checker, ScriptError* serror)
 {
     std::vector<std::vector<unsigned char> > stack;

src/script/interpreter.h

@@ -162,6 +162,17 @@ public:
     virtual ~BaseSignatureChecker() {}
 };
 
+class SimpleSignatureChecker : public BaseSignatureChecker
+{
+private:
+    uint256 hash;
+
+public:
+    const uint256& GetHash() const { return hash; }
+    SimpleSignatureChecker(const uint256& hash_in) : hash(hash_in) {}
+    bool CheckSig(const std::vector<unsigned char>& scriptSig, const std::vector<unsigned char>& vchPubKey, const CScript& scriptCode, SigVersion sigversion) const override;
+};
+
 template <class T>
 class GenericTransactionSignatureChecker : public BaseSignatureChecker
 {

src/script/sign.cpp

@@ -32,6 +32,15 @@ bool MutableTransactionSignatureCreator::CreateSig(const SigningProvider& provid
     return true;
 }
 
+bool SimpleSignatureCreator::CreateSig(const SigningProvider& provider, std::vector<unsigned char>& vchSig, const CKeyID& keyid, const CScript& scriptCode, SigVersion sigversion) const
+{
+    CKey key;
+    if (!provider.GetKey(keyid, key)) return false;
+    if (!key.Sign(checker.GetHash(), vchSig)) return false;
+    vchSig.push_back((unsigned char)SIGHASH_ALL);
+    return true;
+}
+
 static bool GetCScript(const SigningProvider& provider, const SignatureData& sigdata, const CScriptID& scriptid, CScript& script)
 {
     if (provider.GetCScript(scriptid, script)) {

src/script/sign.h

@@ -66,6 +66,16 @@ public:
     virtual bool CreateSig(const SigningProvider& provider, std::vector<unsigned char>& vchSig, const CKeyID& keyid, const CScript& scriptCode, SigVersion sigversion) const =0;
 };
 
+class SimpleSignatureCreator : public BaseSignatureCreator
+{
+    SimpleSignatureChecker checker;
+
+public:
+    SimpleSignatureCreator(const uint256& hashIn) : BaseSignatureCreator(), checker(hashIn) {};
+    const BaseSignatureChecker& Checker() const override { return checker; }
+    bool CreateSig(const SigningProvider& provider, std::vector<unsigned char>& vchSig, const CKeyID& keyid, const CScript& scriptCode, SigVersion sigversion) const override;
+};
+
 /** A signature creator for transactions. */
 class MutableTransactionSignatureCreator : public BaseSignatureCreator {
     const CMutableTransaction* txTo;

src/txdb.cpp

@@ -275,7 +275,10 @@ bool CBlockTreeDB::LoadBlockIndexGuts(const Consensus::Params& consensusParams,
                 pindexNew->nTx            = diskindex.nTx;
 
                 const uint256 block_hash = pindexNew->GetBlockHash();
-                if (!CheckProofOfWork(block_hash, pindexNew->nBits, consensusParams) &&
+                // Block index guts do not include the payload, so we cannot check the POW for
+                // signets here
+                if (!g_solution_blocks &&
+                    !CheckProofOfWork(block_hash, pindexNew->nBits, consensusParams) &&
                     block_hash != consensusParams.hashGenesisBlock) {
                     return error("%s: CheckProofOfWork: %s, %s", __func__, block_hash.ToString(), pindexNew->ToString());
                 }

src/wallet/rpcwallet.cpp

@@ -10,6 +10,7 @@
 #include <httpserver.h>
 #include <validation.h>
 #include <key_io.h>
+#include <miner.h>
 #include <net.h>
 #include <outputtype.h>
 #include <policy/feerate.h>
@@ -3879,6 +3880,187 @@ static UniValue bumpfee(const JSONRPCRequest& request)
     return result;
 }
 
+void SignBlockHashWithWallet(const uint256& hash, CWallet* const pwallet)
+{
+    SignatureData solution_in;
+    if (g_blockheader_payload_map.count(hash) && g_blockheader_payload_map.at(hash).size()) {
+        solution_in = SignatureData(CScript(g_blockheader_payload_map[hash].begin(), g_blockheader_payload_map[hash].end()));
+    }
+    CScript blockscript(Params().GetConsensus().blockscript.begin(), Params().GetConsensus().blockscript.end());
+    size_t siglen = gArgs.GetArg("-signet_siglen", 0);
+
+    // sign until we have a sufficiently small signature, or until we run out of tries
+    bool res;
+    size_t smallest = 9999;
+    std::vector<uint8_t> sigdata;
+    size_t overhead = GetSizeOfCompactSize(siglen);
+    for (size_t i = 0; i < 1000; ++i) {
+        SignatureData solution(solution_in);
+        res = ProduceSignature(*pwallet, SimpleSignatureCreator(hash), blockscript, solution);
+        if (!res) {
+            throw JSONRPCError(RPC_VERIFY_ERROR, "could not produce a signature -- do you have the private key(s)?");
+        }
+        if (solution.scriptSig.size() < smallest) {
+            smallest = solution.scriptSig.size();
+            if (!siglen || smallest + overhead <= siglen) {
+                sigdata = std::vector<uint8_t>(solution.scriptSig.begin(), solution.scriptSig.end());
+                break;
+            }
+        }
+    }
+    if (siglen && sigdata.size() == 0) {
+        throw JSONRPCError(RPC_VERIFY_ERROR, strprintf("unable to produce a signature of size <= %zu (smallest found was %zu)", siglen, smallest + overhead));
+    }
+
+    g_blockheader_payload_map[hash] = sigdata;
+}
+
+UniValue signblock(const JSONRPCRequest& request)
+{
+    std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
+    CWallet* const pwallet = wallet.get();
+
+    if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
+        return NullUniValue;
+    }
+
+    if (!g_solution_blocks) {
+        throw std::runtime_error(
+            "signblock can only be used with signet networks"
+        );
+    }
+
+    if (request.fHelp || request.params.size() != 1) {
+        throw std::runtime_error(
+            "signblock \"blockhex\"\n"
+            "\nSigns a block proposal, checking that it would be accepted first\n"
+            "\nArguments:\n"
+            "1. \"blockhex\"    (string, required) The hex-encoded block from getnewblockhex\n"
+            "\nResult\n"
+            " sig      (hex) The signature\n"
+            "\nExamples:\n"
+            + HelpExampleCli("signblock", "0000002018c6f2f913f9902aeab...5ca501f77be96de63f609010000000000000000015100000000")
+        );
+    }
+
+    CBlock block;
+    if (!DecodeHexBlk(block, request.params[0].get_str())) {
+        throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "Block decode failed");
+    }
+
+    LOCK(cs_main);
+
+    uint256 hash = block.GetHash();
+    BlockMap::iterator mi = mapBlockIndex.find(hash);
+    if (mi != mapBlockIndex.end()) {
+        throw JSONRPCError(RPC_VERIFY_ERROR, "already have block");
+    }
+
+    CBlockIndex* const pindexPrev = chainActive.Tip();
+    // TestBlockValidity only supports blocks built on the current Tip
+    if (block.hashPrevBlock != pindexPrev->GetBlockHash()) {
+        throw JSONRPCError(RPC_VERIFY_ERROR, "proposal was not based on our best chain");
+    }
+
+    CValidationState state;
+    if (!TestBlockValidity(state, Params(), block, pindexPrev, false, true) || !state.IsValid()) {
+        std::string strRejectReason = state.GetRejectReason();
+        if (strRejectReason.empty()) {
+            throw JSONRPCError(RPC_VERIFY_ERROR, state.IsInvalid() ? "Block proposal was invalid" : "Error checking block proposal");
+        }
+        throw JSONRPCError(RPC_VERIFY_ERROR, strRejectReason);
+    }
+    SignBlockHashWithWallet(hash, pwallet);
+    return HexStr(g_blockheader_payload_map.at(hash));
+}
+
+UniValue getnewblockhex(const JSONRPCRequest& request)
+{
+    std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
+    CWallet* const pwallet = wallet.get();
+
+    if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
+        return NullUniValue;
+    }
+
+    if (request.fHelp || request.params.size() > 1) {
+        throw std::runtime_error(
+            "getnewblockhex ( broadcast )\n"
+            "\nGets hex representation of a proposed, unmined new block, optionally\n"
+            "signing and broadcasting it to the network.\n"
+            "\nArguments:\n"
+            "1. broadcast    (boolean, optional, default=false) Sign and broadcast the block immediately, returning the blockhash\n"
+            "\nResult (for broadcast=false)\n"
+            "blockhex      (hex) The block hex\n"
+            "\nResult (for broadcast=true)\n"
+            "blockhash     (hash) The block hash\n"
+            "\nExamples:\n"
+            + HelpExampleCli("getnewblockhex", "")
+            + HelpExampleCli("getnewblockhex", "true")
+        );
+    }
+
+    bool broadcast = !request.params[0].isNull() && request.params[0].get_bool();
+
+    std::shared_ptr<CReserveScript> coinbase_script;
+    pwallet->GetScriptForMining(coinbase_script);
+
+    // If the keypool is exhausted, no script is returned at all.  Catch this.
+    if (!coinbase_script) {
+        throw JSONRPCError(RPC_WALLET_KEYPOOL_RAN_OUT, "Error: Keypool ran out, please call keypoolrefill first");
+    }
+
+    //throw an error if no script was provided
+    if (coinbase_script->reserveScript.empty()) {
+        throw JSONRPCError(RPC_INTERNAL_ERROR, "No coinbase script available");
+    }
+
+    std::unique_ptr<CBlockTemplate> pblocktemplate(BlockAssembler(Params()).CreateNewBlock(coinbase_script->reserveScript));
+    {
+        // IncrementExtraNonce sets coinbase flags and builds merkle tree
+        LOCK(cs_main);
+        unsigned int nExtraNonce = 0;
+        IncrementExtraNonce(&pblocktemplate->block, chainActive.Tip(), nExtraNonce);
+    }
+
+    CDataStream ssBlock(SER_NETWORK, PROTOCOL_VERSION);
+    ssBlock << pblocktemplate->block;
+
+    if (broadcast) {
+        // attempt to sign
+        uint256 hash = pblocktemplate->block.GetHash();
+        SignBlockHashWithWallet(hash, pwallet);
+        // and submit
+        UniValue submitblock(const JSONRPCRequest& request);
+        UniValue params(UniValue::VARR);
+        params.push_back(HexStr(ssBlock.begin(), ssBlock.end()));
+        params.push_back(HexStr(g_blockheader_payload_map.at(hash).begin(), g_blockheader_payload_map.at(hash).end()));
+        JSONRPCRequest req;
+        req.params = params;
+        submitblock(req);
+        return HexStr(hash);
+    }
+
+    return HexStr(ssBlock.begin(), ssBlock.end());
+}
+
+UniValue GenerateSignetBlocks(int count)
+{
+    UniValue params(UniValue::VARR);
+    UniValue t(UniValue::VBOOL);
+    t.setBool(true);
+    params.push_back(t);
+    JSONRPCRequest req;
+    req.params = params;
+
+    UniValue blockHashes(UniValue::VARR);
+    for (int i = 0; i < count; ++i) {
+        blockHashes.push_back(getnewblockhex(req));
+    }
+
+    return blockHashes;
+}
+
 UniValue generate(const JSONRPCRequest& request)
 {
     std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
@@ -3905,6 +4087,11 @@ UniValue generate(const JSONRPCRequest& request)
     }
 
     int num_generate = request.params[0].get_int();
+
+    if (g_solution_blocks) {
+        return GenerateSignetBlocks(num_generate);
+    }
+
     uint64_t max_tries = 1000000;
     if (!request.params[1].isNull()) {
         max_tries = request.params[1].get_int();
@@ -4838,6 +5025,10 @@ static const CRPCCommand commands[] =
     { "wallet",             "setlabel",                         &setlabel,                      {"address","label"} },
 
     { "generating",         "generate",                         &generate,                      {"nblocks","maxtries"} },
+
+    /** Signet mining */
+    { "wallet",             "signblock",                        &signblock,                     {"blockhex"} },
+    { "wallet",             "getnewblockhex",                   &getnewblockhex,                {"broadcast"} },
 };
 
 void RegisterWalletRPCCommands(CRPCTable &t)

test/functional/feature_genesishash.py

@@ -28,6 +28,25 @@ GENESIS_ARGS_MAP = [
         ],
     },
 
+    {
+        'memo': 'default_style with blockscript',
+        'genesis': 'ac6b1de55f8cb2cffc12c0cab0036d0966a6142fd5f70d0d0ecd96b56f4cb1b6',
+        'args': [
+                '-con_genesis_style=default_style',
+                '-signet_blockscript=512103e464a9f3070da4d3e0b34ce971ff36f3e07c47a8f4beadf32e8ea7e2afa8a82451ae',
+        ],
+    },
+
+    {
+        'memo': 'signet_old',
+        'genesis': '7cbf2772cb0e53345b021f34d17b30de42a8952c982b0812e4caca7529009ca5',
+        # TODO FIXME Should be
+        # 'genesis': '22861f488a5c6cb033a843e476581a8abf5b82a34926babfde1241ed97ba268e',
+        'args': [
+                '-con_genesis_style=signet_old',
+                '-signet_blockscript=512103e464a9f3070da4d3e0b34ce971ff36f3e07c47a8f4beadf32e8ea7e2afa8a82451ae',
+        ],
+    },
 ]
 
 class GenesisHashTest(BitcoinTestFramework):

test/functional/test_framework/mininode.py

@@ -54,6 +54,7 @@ MAGIC_BYTES = {
     "mainnet": b"\xf9\xbe\xb4\xd9",   # mainnet
     "testnet3": b"\x0b\x11\x09\x07",  # testnet3
     "regtest": b"\xfa\xbf\xb5\xda",   # regtest
+    "signet":  b"\xf0\xc7\x70\x6a",   # signet
 }