File.Human() option to print partial results.

LICENSE

@@ -0,0 +1,7 @@
+This is free and unencumbered software released into the public domain.
+
+Anyone is free to copy, modify, publish, use, compile, sell, or distribute this software, either in source code form or as a compiled binary, for any purpose, commercial or non-commercial, and by any means.
+
+In jurisdictions that recognize copyright laws, the author or authors of this software dedicate any and all copyright interest in the software to the public domain. We make this dedication for the benefit of the public at large and to the detriment of our heirs and successors. We intend this dedication to be an overt act of relinquishment in perpetuity of all present and future rights to this software under copyright law.
+
+THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

README.md

@@ -16,8 +16,8 @@ func main () {
     hash := sha256.Sum256([]byte{1,2,3,4,5,6})
     seq, _ := opentimestamps.Stamp(context.Background(), "https://alice.btc.calendar.opentimestamps.org/", hash)
 
-    // you can just call .Upgrade() to get the upgraded sequence (or an error if not yet available)
-    upgradedSeq, err := seq.Upgrade(context.Background(), hash[:])
+    // you can just call UpgradeSequence() to get the upgraded sequence (or an error if not yet available)
+    upgradedSeq, err := opentimestamps.UpgradeSequence(context.Background(), seq, hash[:])
     if err != nil {
         fmt.Println("wait more")
     }
@@ -43,7 +43,7 @@ func main () {
     fmt.Println(hex.EncodeToString(seq[2].Argument)) // "c40fe258f9b828a0b5a7"
 
     // all these instructions can be executed in order, starting from the initial hash
-    result := seq.Compute(hash) // this is the value we send to the calendar server in order to get the upgraded sequence on .Upgrade()
+    result := seq.Compute(hash) // this is the value we send to the calendar server in order to get the upgraded sequence
     finalResult := upgradedSeq.Compute(hash) // this should be the merkle root of a bitcoin block if this sequence is upgraded
 
     // each sequence always ends in an "attestation"

esplora.go

@@ -9,9 +9,10 @@ import (
 	"strconv"
 	"strings"
 
+	"slices"
+
 	"github.com/btcsuite/btcd/chaincfg/chainhash"
 	"github.com/btcsuite/btcd/wire"
-	"golang.org/x/exp/slices"
 )
 
 func NewEsploraClient(url string) Bitcoin {

go.mod

@@ -6,7 +6,6 @@ require (
 	github.com/btcsuite/btcd v0.23.4
 	github.com/btcsuite/btcd/chaincfg/chainhash v1.0.1
 	golang.org/x/crypto v0.13.0
-	golang.org/x/exp v0.0.0-20230905200255-921286631fa9
 )
 
 require (

go.sum

@@ -66,8 +66,6 @@ golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACk
 golang.org/x/crypto v0.0.0-20200622213623-75b288015ac9/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
 golang.org/x/crypto v0.13.0 h1:mvySKfSWJ+UKUii46M40LOvyWfN0s2U+46/jDd0e6Ck=
 golang.org/x/crypto v0.13.0/go.mod h1:y6Z2r+Rw4iayiXXAIxJIDAJ1zMW4yaTpebo8fPOliYc=
-golang.org/x/exp v0.0.0-20230905200255-921286631fa9 h1:GoHiUyI/Tp2nVkLI2mCxVkOjsbSXD66ic0XW0js0R9g=
-golang.org/x/exp v0.0.0-20230905200255-921286631fa9/go.mod h1:S2oDrQGGwySpoQPVqRShND87VCbxmc6bL1Yd2oYrm6k=
 golang.org/x/net v0.0.0-20180719180050-a680a1efc54d/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
 golang.org/x/net v0.0.0-20180906233101-161cd47e91fd/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
 golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=

helpers.go

@@ -3,7 +3,7 @@ package opentimestamps
 import (
 	"strings"
 
-	"golang.org/x/exp/slices"
+	"slices"
 )
 
 // CompareInstructions returns negative if a<b, 0 if a=b and positive if a>b.

ots.go

@@ -1,12 +1,14 @@
 package opentimestamps
 
 import (
+	"bytes"
 	"crypto/sha256"
 	"encoding/hex"
 	"fmt"
+	"slices"
 	"strings"
 
-	"golang.org/x/exp/slices"
+	"github.com/btcsuite/btcd/wire"
 )
 
 /*
@@ -71,15 +73,40 @@ type Instruction struct {
 
 type Sequence []Instruction
 
-func (seq Sequence) Compute(initial []byte) []byte {
+func (seq Sequence) GetAttestation() Attestation {
+	if len(seq) == 0 {
+		return Attestation{}
+	}
+	att := seq[len(seq)-1]
+	if att.Attestation == nil {
+		return Attestation{}
+	}
+	return *att.Attestation
+}
+
+// Compute runs a sequence of operations on top of an initial digest and returns the result, which is often a
+// Bitcoin block merkle root. It also tries to identify the point in the sequence in which an actual Bitcoin
+// transaction is formed and parse that.
+func (seq Sequence) Compute(initial []byte) (merkleRoot []byte, bitcoinTx *wire.MsgTx) {
 	current := initial
-	for _, inst := range seq {
+	for i, inst := range seq {
 		if inst.Operation == nil {
 			break
 		}
+
+		// the first time we do a double-sha256 that is likely a bitcoin transaction
+		if bitcoinTx == nil &&
+			inst.Operation.Name == "sha256" &&
+			len(seq) > i+1 && seq[i+1].Operation != nil &&
+			seq[i+1].Operation.Name == "sha256" {
+			tx := &wire.MsgTx{}
+			tx.Deserialize(bytes.NewReader(current))
+			bitcoinTx = tx
+		}
+
 		current = inst.Operation.Apply(current, inst.Argument)
 	}
-	return current
+	return current, bitcoinTx
 }
 
 func (ts File) GetPendingSequences() []Sequence {
@@ -122,20 +149,26 @@ func (ts File) GetBitcoinAttestedSequences() []Sequence {
 	return results
 }
 
-func (ts File) Human() string {
+func (ts File) Human(withPartials bool) string {
 	strs := make([]string, 0, 100)
 	strs = append(strs, fmt.Sprintf("file digest: %x", ts.Digest))
 	strs = append(strs, fmt.Sprintf("hashed with: sha256"))
 	strs = append(strs, "instruction sequences:")
 	for _, seq := range ts.Sequences {
+		curr := ts.Digest
 		strs = append(strs, "~>")
+		strs = append(strs, "  start "+hex.EncodeToString(curr))
 		for _, inst := range seq {
 			line := "  "
 			if inst.Operation != nil {
 				line += inst.Operation.Name
+				curr = inst.Operation.Apply(curr, inst.Argument)
 				if inst.Operation.Binary {
 					line += " " + hex.EncodeToString(inst.Argument)
 				}
+				if withPartials {
+					line += " = " + hex.EncodeToString(curr)
+				}
 			} else if inst.Attestation != nil {
 				line += inst.Attestation.Human()
 			} else {

parsers.go

@@ -4,7 +4,7 @@ import (
 	"fmt"
 	"io"
 
-	"golang.org/x/exp/slices"
+	"slices"
 )
 
 func parseCalendarServerResponse(buf Buffer) (Sequence, error) {

stamp.go

@@ -41,9 +41,9 @@ func ReadFromFile(data []byte) (*File, error) {
 	return parseOTSFile(newBuffer(data))
 }
 
-func (seq Sequence) Upgrade(ctx context.Context, initial []byte) (Sequence, error) {
-	result := seq.Compute(initial)
-	attestation := seq[len(seq)-1]
+func UpgradeSequence(ctx context.Context, seq Sequence, initial []byte) (Sequence, error) {
+	result, _ := seq.Compute(initial)
+	attestation := seq.GetAttestation()
 
 	url := fmt.Sprintf("%s/timestamp/%x", normalizeUrl(attestation.CalendarServerURL), result)
 	req, err := http.NewRequestWithContext(ctx, "GET", url, nil)
@@ -69,10 +69,14 @@ func (seq Sequence) Upgrade(ctx context.Context, initial []byte) (Sequence, erro
 	}
 	resp.Body.Close()
 
-	newSeq, err := parseCalendarServerResponse(newBuffer(body))
+	tail, err := parseCalendarServerResponse(newBuffer(body))
 	if err != nil {
 		return nil, fmt.Errorf("failed to parse response from '%s': %w", attestation.CalendarServerURL, err)
 	}
 
+	newSeq := make(Sequence, len(seq)+len(tail)-1)
+	copy(newSeq, seq[0:len(seq)-1])
+	copy(newSeq[len(seq)-1:], tail)
+
 	return newSeq, nil
 }

verifier.go

@@ -1,11 +1,11 @@
 package opentimestamps
 
 import (
+	"bytes"
 	"fmt"
 
 	"github.com/btcsuite/btcd/chaincfg/chainhash"
 	"github.com/btcsuite/btcd/wire"
-	"golang.org/x/exp/slices"
 )
 
 type Bitcoin interface {
@@ -13,33 +13,35 @@ type Bitcoin interface {
 	GetBlockHeader(hash *chainhash.Hash) (*wire.BlockHeader, error)
 }
 
-func (seq Sequence) Verify(bitcoin Bitcoin, initial []byte) error {
+// Verify validates sequence of operations that starts with digest and ends on a Bitcoin attestation against
+// an actual Bitcoin block, as given by the provided Bitcoin interface.
+func (seq Sequence) Verify(bitcoin Bitcoin, digest []byte) (*wire.MsgTx, error) {
 	if len(seq) == 0 {
-		return fmt.Errorf("empty sequence")
+		return nil, fmt.Errorf("empty sequence")
 	}
 
 	att := seq[len(seq)-1]
 	if att.Attestation == nil || att.BitcoinBlockHeight == 0 {
-		return fmt.Errorf("sequence doesn't include a bitcoin attestation")
+		return nil, fmt.Errorf("sequence doesn't include a bitcoin attestation")
 	}
 
 	blockHash, err := bitcoin.GetBlockHash(int64(att.BitcoinBlockHeight))
 	if err != nil {
-		return fmt.Errorf("failed to get block %d hash: %w", att.BitcoinBlockHeight, err)
+		return nil, fmt.Errorf("failed to get block %d hash: %w", att.BitcoinBlockHeight, err)
 	}
 
 	blockHeader, err := bitcoin.GetBlockHeader(blockHash)
 	if err != nil {
-		return fmt.Errorf("failed to get block %s header: %w", blockHash, err)
+		return nil, fmt.Errorf("failed to get block %s header: %w", blockHash, err)
 	}
 
 	merkleRoot := blockHeader.MerkleRoot[:]
+	result, tx := seq.Compute(digest)
 
-	result := seq.Compute(initial)
-	if !slices.Equal(result, merkleRoot) {
-		return fmt.Errorf("sequence result '%x' doesn't match the bitcoin merkle root for block %d: %x",
+	if !bytes.Equal(result, merkleRoot) {
+		return nil, fmt.Errorf("sequence result '%x' doesn't match the bitcoin merkle root for block %d: %x",
 			result, att.BitcoinBlockHeight, merkleRoot)
 	}
 
-	return nil
+	return tx, nil
 }