StateProofs: New block header field - SHA256 merkle root of the trans…

…actions (#3829)

Currently, the TxnRoot block header contains the root of the merkle tree
built from the transactions in the block, using the SHA512_256 hash function.
Since the Ethereum VM (and others) does not support SHA512_256 natively,
we have added a new header, which will be used by the Light Clients
deployed on other networks in order to verify Algorand blocks.

Co-authored-by: algoidan <79864820+algoidan@users.noreply.github.com>

catchup/fetcher_test.go

@@ -105,7 +105,7 @@ func buildTestLedger(t *testing.T, blk bookkeeping.Block) (ledger *data.Ledger,
 	b.Payset = []transactions.SignedTxnInBlock{
 		txib,
 	}
-	b.TxnRoot, err = b.PaysetCommit()
+	b.TxnCommitments, err = b.PaysetCommit()
 	require.NoError(t, err)
 	require.NoError(t, ledger.AddBlock(b, agreement.Certificate{Round: next}))
 	return
@@ -116,7 +116,7 @@ func addBlocks(t *testing.T, ledger *data.Ledger, blk bookkeeping.Block, numBloc
 	for i := 0; i < numBlocks; i++ {
 		blk.BlockHeader.Round++
 		blk.BlockHeader.TimeStamp += int64(crypto.RandUint64() % 100 * 1000)
-		blk.TxnRoot, err = blk.PaysetCommit()
+		blk.TxnCommitments, err = blk.PaysetCommit()
 		require.NoError(t, err)
 
 		err := ledger.AddBlock(blk, agreement.Certificate{Round: blk.BlockHeader.Round})

config/consensus.go

@@ -435,6 +435,11 @@ type ConsensusParams struct {
 
 	// UnifyInnerTxIDs enables a consistent, unified way of computing inner transaction IDs
 	UnifyInnerTxIDs bool
+
+	// EnableSHA256TxnCommitmentHeader enables the creation of a transaction vector commitment tree using SHA256 hash function. (vector commitment extends Merkle tree by having a position binding property).
+	// This new header is in addition to the existing SHA512_256 merkle root.
+	// It is useful for verifying transaction on different blockchains, as some may not support SHA512_256 OPCODE natively but SHA256 is common.
+	EnableSHA256TxnCommitmentHeader bool
 }
 
 // PaysetCommitType enumerates possible ways for the block header to commit to
@@ -1144,6 +1149,8 @@ func initConsensusProtocols() {
 
 	vFuture.UnifyInnerTxIDs = true
 
+	vFuture.EnableSHA256TxnCommitmentHeader = true
+
 	Consensus[protocol.ConsensusFuture] = vFuture
 }
 

crypto/compactcert/structs.go

@@ -25,7 +25,7 @@ import (
 
 // Params defines common parameters for the verifier and builder.
 type Params struct {
-	Msg          crypto.Hashable // Message to be cerified
+	Msg          crypto.Hashable // Message to be certified
 	ProvenWeight uint64          // Weight threshold proven by the certificate
 	SigRound     basics.Round    // The round for which the ephemeral key is committed to
 	SecKQ        uint64          // Security parameter (k+q) from analysis document

crypto/hashes.go

@@ -17,6 +17,7 @@
 package crypto
 
 import (
+	"crypto/sha256"
 	"crypto/sha512"
 	"errors"
 	"fmt"
@@ -41,7 +42,7 @@ func (h HashType) Validate() error {
 const (
 	Sha512_256 HashType = iota
 	Sumhash
-
+	Sha256
 	MaxHashType
 )
 
@@ -53,6 +54,7 @@ const MaxHashDigestSize = SumhashDigestSize
 const (
 	Sha512_256Size    = sha512.Size256
 	SumhashDigestSize = sumhash.Sumhash512DigestSize
+	Sha256Size        = sha256.Size
 )
 
 // HashFactory is responsible for generating new hashes accordingly to the type it stores.
@@ -71,6 +73,8 @@ func (h HashType) String() string {
 		return "sha512_256"
 	case Sumhash:
 		return "sumhash"
+	case Sha256:
+		return "sha256"
 	default:
 		return ""
 	}
@@ -83,6 +87,8 @@ func UnmarshalHashType(s string) (HashType, error) {
 		return Sha512_256, nil
 	case "sumhash":
 		return Sumhash, nil
+	case "sha256":
+		return Sha256, nil
 	default:
 		return 0, fmt.Errorf("HashType not supported: %s", s)
 	}
@@ -96,6 +102,8 @@ func (z HashFactory) NewHash() hash.Hash {
 		return sha512.New512_256()
 	case Sumhash:
 		return sumhash.New512(nil)
+	case Sha256:
+		return sha256.New()
 	// This shouldn't be reached, when creating a new hash, one would know the type of hash they wanted,
 	// in addition to that, unmarshalling of the hashFactory verifies the HashType of the factory.
 	default:

crypto/hashes_test.go

@@ -37,6 +37,9 @@ func TestHashFactoryCreatingNewHashes(t *testing.T) {
 	a.NotNil(h)
 	a.Equal(SumhashDigestSize, h.Size())
 
+	h = HashFactory{HashType: Sha256}.NewHash()
+	a.NotNil(h)
+	a.Equal(Sha256Size, h.Size())
 }
 
 func TestHashSum(t *testing.T) {