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Updates Go's implementation for bech32m. #68

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Updates Go's implementation for bech32m. #68

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71 changes: 53 additions & 18 deletions ref/go/src/bech32/bech32.go
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Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,13 @@ import (
"strings"
)

const (
encBech32 = 1
encBech32m = 2
invalidEncoding = -1
bech32mConst = 0x2bc830a3
)

var charset = "qpzry9x8gf2tvdw0s3jn54khce6mua7l"

var generator = []int{0x3b6a57b2, 0x26508e6d, 0x1ea119fa, 0x3d4233dd, 0x2a1462b3}
Expand Down Expand Up @@ -56,13 +63,26 @@ func hrpExpand(hrp string) []int {
return ret
}

func verifyChecksum(hrp string, data []int) bool {
return polymod(append(hrpExpand(hrp), data...)) == 1
func verifyChecksum(hrp string, data []int) int {
constant := polymod(append(hrpExpand(hrp), data...))
if constant == 1 {
return encBech32
} else if constant == bech32mConst {
return encBech32m
}

return invalidEncoding
}

func createChecksum(hrp string, data []int) []int {
func createChecksum(hrp string, data []int, spec int) []int {
values := append(append(hrpExpand(hrp), data...), []int{0, 0, 0, 0, 0, 0}...)
mod := polymod(values) ^ 1
constant := 1
if spec == encBech32m {
constant = bech32mConst
}

mod := polymod(values) ^ constant

ret := make([]int, 6)
for p := 0; p < len(ret); p++ {
ret[p] = (mod >> uint(5*(5-p))) & 31
Expand All @@ -72,7 +92,7 @@ func createChecksum(hrp string, data []int) []int {

// Encode encodes hrp(human-readable part) and data(32bit data array), returns Bech32 / or error
// if hrp is uppercase, return uppercase Bech32
func Encode(hrp string, data []int) (string, error) {
func Encode(hrp string, data []int, spec int) (string, error) {
if (len(hrp) + len(data) + 7) > 90 {
return "", fmt.Errorf("too long : hrp length=%d, data length=%d", len(hrp), len(data))
}
Expand All @@ -89,7 +109,7 @@ func Encode(hrp string, data []int) (string, error) {
}
lower := strings.ToLower(hrp) == hrp
hrp = strings.ToLower(hrp)
combined := append(data, createChecksum(hrp, data)...)
combined := append(data, createChecksum(hrp, data, spec)...)
var ret bytes.Buffer
ret.WriteString(hrp)
ret.WriteString("1")
Expand All @@ -105,37 +125,39 @@ func Encode(hrp string, data []int) (string, error) {
return strings.ToUpper(ret.String()), nil
}

// Decode decodes bechString(Bech32) returns hrp(human-readable part) and data(32bit data array) / or error
func Decode(bechString string) (string, []int, error) {
// Decode decodes bechString(Bech32/Bech32m) returns hrp(human-readable part), data(32bit data array) and spec (int) / or error
func Decode(bechString string) (string, []int, int, error) {
if len(bechString) > 90 {
return "", nil, fmt.Errorf("too long : len=%d", len(bechString))
return "", nil, invalidEncoding, fmt.Errorf("too long : len=%d", len(bechString))
}
if strings.ToLower(bechString) != bechString && strings.ToUpper(bechString) != bechString {
return "", nil, fmt.Errorf("mixed case")
return "", nil, invalidEncoding, fmt.Errorf("mixed case")
}
bechString = strings.ToLower(bechString)
pos := strings.LastIndex(bechString, "1")
if pos < 1 || pos+7 > len(bechString) {
return "", nil, fmt.Errorf("separator '1' at invalid position : pos=%d , len=%d", pos, len(bechString))
return "", nil, invalidEncoding, fmt.Errorf("separator '1' at invalid position : pos=%d , len=%d", pos, len(bechString))
}
hrp := bechString[0:pos]
for p, c := range hrp {
if c < 33 || c > 126 {
return "", nil, fmt.Errorf("invalid character human-readable part : bechString[%d]=%d", p, c)
return "", nil, invalidEncoding, fmt.Errorf("invalid character human-readable part : bechString[%d]=%d", p, c)
}
}
data := []int{}
for p := pos + 1; p < len(bechString); p++ {
d := strings.Index(charset, fmt.Sprintf("%c", bechString[p]))
if d == -1 {
return "", nil, fmt.Errorf("invalid character data part : bechString[%d]=%d", p, bechString[p])
return "", nil, invalidEncoding, fmt.Errorf("invalid character data part : bechString[%d]=%d", p, bechString[p])
}
data = append(data, d)
}
if !verifyChecksum(hrp, data) {
return "", nil, fmt.Errorf("invalid checksum")

spec := verifyChecksum(hrp, data)
if spec == invalidEncoding {
return "", nil, invalidEncoding, fmt.Errorf("invalid checksum")
}
return hrp, data[:len(data)-6], nil
return hrp, data[:len(data)-6], spec, nil
}

func convertbits(data []int, frombits, tobits uint, pad bool) ([]int, error) {
Expand Down Expand Up @@ -168,7 +190,7 @@ func convertbits(data []int, frombits, tobits uint, pad bool) ([]int, error) {

// SegwitAddrDecode decodes hrp(human-readable part) Segwit Address(string), returns version(int) and data(bytes array) / or error
func SegwitAddrDecode(hrp, addr string) (int, []int, error) {
dechrp, data, err := Decode(addr)
dechrp, data, spec, err := Decode(addr)
if err != nil {
return -1, nil, err
}
Expand All @@ -191,11 +213,19 @@ func SegwitAddrDecode(hrp, addr string) (int, []int, error) {
if data[0] == 0 && len(res) != 20 && len(res) != 32 {
return -1, nil, fmt.Errorf("invalid program length for witness version 0 (per BIP141) : %d", len(res))
}
if data[0] == 0 && spec != encBech32 || data[0] != 0 && spec != encBech32m {
return -1, nil, fmt.Errorf("witness version and encoding don't match : %d and %d", data[0], spec)
}
return data[0], res, nil
}

// SegwitAddrEncode encodes hrp(human-readable part) , version(int) and data(bytes array), returns Segwit Address / or error
func SegwitAddrEncode(hrp string, version int, program []int) (string, error) {
spec := encBech32m
if version == 0 {
spec = encBech32
}

if version < 0 || version > 16 {
return "", fmt.Errorf("invalid witness version : %d", version)
}
Expand All @@ -205,11 +235,16 @@ func SegwitAddrEncode(hrp string, version int, program []int) (string, error) {
if version == 0 && len(program) != 20 && len(program) != 32 {
return "", fmt.Errorf("invalid program length for witness version 0 (per BIP141) : %d", len(program))
}
if version == 0 && spec != encBech32 || version != 0 && spec != encBech32m {
return "", fmt.Errorf("witness version and encoding don't match : %d and %d", version, spec)
}

data, err := convertbits(program, 8, 5, true)
if err != nil {
return "", err
}
ret, err := Encode(hrp, append([]int{version}, data...))

ret, err := Encode(hrp, append([]int{version}, data...), spec)
if err != nil {
return "", err
}
Expand Down
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