95 lines
2.3 KiB
Go
95 lines
2.3 KiB
Go
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package emojihash
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import (
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"bufio"
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"bytes"
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"errors"
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"math/big"
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"strings"
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"github.com/status-im/status-go/protocol/identity"
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"github.com/status-im/status-go/static"
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)
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const (
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emojiAlphabetLen = 2757 // 20bytes of data described by 14 emojis requires at least 2757 length alphabet
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emojiHashLen = 14
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)
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var emojisAlphabet []string
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func GenerateFor(pubkey string) ([]string, error) {
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if len(emojisAlphabet) == 0 {
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alphabet, err := loadAlphabet()
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if err != nil {
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return nil, err
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}
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emojisAlphabet = *alphabet
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}
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compressedKey, err := identity.ToCompressedKey(pubkey)
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if err != nil {
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return nil, err
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}
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slices, err := identity.Slices(compressedKey)
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if err != nil {
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return nil, err
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}
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return toEmojiHash(new(big.Int).SetBytes(slices[1]), emojiHashLen, &emojisAlphabet)
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}
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func loadAlphabet() (*[]string, error) {
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data, err := static.Asset("emojis.txt")
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if err != nil {
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return nil, err
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}
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alphabet := make([]string, 0, emojiAlphabetLen)
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scanner := bufio.NewScanner(bytes.NewReader(data))
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for scanner.Scan() {
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alphabet = append(alphabet, strings.Replace(scanner.Text(), "\n", "", -1))
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}
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// current alphabet contains more emojis than needed, just in case some emojis needs to be removed
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// make sure only necessary part is loaded
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if len(alphabet) > emojiAlphabetLen {
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alphabet = alphabet[:emojiAlphabetLen]
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}
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return &alphabet, nil
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}
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func toEmojiHash(value *big.Int, hashLen int, alphabet *[]string) (hash []string, err error) {
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valueBitLen := value.BitLen()
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alphabetLen := new(big.Int).SetInt64(int64(len(*alphabet)))
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indexes := identity.ToBigBase(value, alphabetLen.Uint64())
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if hashLen == 0 {
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hashLen = len(indexes)
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} else if hashLen > len(indexes) {
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prependLen := hashLen - len(indexes)
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for i := 0; i < prependLen; i++ {
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indexes = append([](uint64){0}, indexes...)
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}
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}
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// alphabetLen^hashLen
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possibleCombinations := new(big.Int).Exp(alphabetLen, new(big.Int).SetInt64(int64(hashLen)), nil)
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// 2^valueBitLen
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requiredCombinations := new(big.Int).Exp(new(big.Int).SetInt64(2), new(big.Int).SetInt64(int64(valueBitLen)), nil)
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if possibleCombinations.Cmp(requiredCombinations) == -1 {
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return nil, errors.New("alphabet or hash length is too short to encode given value")
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}
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for _, v := range indexes {
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hash = append(hash, (*alphabet)[v])
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}
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return hash, nil
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}
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