package common import ( "bytes" "encoding/binary" "fmt" "math/big" ethCommon "github.com/ethereum/go-ethereum/common" "github.com/iden3/go-iden3-crypto/babyjub" "github.com/iden3/go-iden3-crypto/poseidon" cryptoUtils "github.com/iden3/go-iden3-crypto/utils" ) const ( // NLeafElems is the number of elements for a leaf NLeafElems = 4 // maxNonceValue is the maximum value that the Account.Nonce can have (40 bits: maxNonceValue=2**40-1) maxNonceValue = 0xffffffffff // maxBalanceBytes is the maximum bytes that can use the Account.Balance *big.Int maxBalanceBytes = 24 ) // Account is a struct that gives information of the holdings of an address and a specific token. Is the data structure that generates the Value stored in the leaf of the MerkleTree type Account struct { TokenID TokenID Nonce Nonce // max of 40 bits used Balance *big.Int // max of 192 bits used PublicKey *babyjub.PublicKey EthAddr ethCommon.Address } func (a *Account) String() string { buf := bytes.NewBufferString("") fmt.Fprintf(buf, "PublicKey: %s..., ", a.PublicKey.String()[:10]) fmt.Fprintf(buf, "EthAddr: %s..., ", a.EthAddr.String()[:10]) fmt.Fprintf(buf, "TokenID: %v, ", a.TokenID) fmt.Fprintf(buf, "Nonce: %d, ", a.Nonce) fmt.Fprintf(buf, "Balance: %s, ", a.Balance.String()) return buf.String() } // Bytes returns the bytes representing the Account, in a way that each BigInt is represented by 32 bytes, in spite of the BigInt could be represented in less bytes (due a small big.Int), so in this way each BigInt is always 32 bytes and can be automatically parsed from a byte array. func (a *Account) Bytes() ([32 * NLeafElems]byte, error) { var b [32 * NLeafElems]byte if a.Nonce > maxNonceValue { return b, fmt.Errorf("%s Nonce", ErrNumOverflow) } if len(a.Balance.Bytes()) > maxBalanceBytes { return b, fmt.Errorf("%s Balance", ErrNumOverflow) } nonceBytes, err := a.Nonce.Bytes() if err != nil { return b, err } copy(b[0:4], a.TokenID.Bytes()) copy(b[4:9], nonceBytes[:]) if babyjub.PointCoordSign(a.PublicKey.X) { b[10] = 1 } copy(b[32:64], SwapEndianness(a.Balance.Bytes())) // SwapEndianness, as big.Int uses BigEndian copy(b[64:96], SwapEndianness(a.PublicKey.Y.Bytes())) copy(b[96:116], a.EthAddr.Bytes()) return b, nil } // BigInts returns the [5]*big.Int, where each *big.Int is inside the Finite Field func (a *Account) BigInts() ([NLeafElems]*big.Int, error) { e := [NLeafElems]*big.Int{} b, err := a.Bytes() if err != nil { return e, err } e[0] = new(big.Int).SetBytes(SwapEndianness(b[0:32])) e[1] = new(big.Int).SetBytes(SwapEndianness(b[32:64])) e[2] = new(big.Int).SetBytes(SwapEndianness(b[64:96])) e[3] = new(big.Int).SetBytes(SwapEndianness(b[96:128])) return e, nil } // HashValue returns the value of the Account, which is the Poseidon hash of its *big.Int representation func (a *Account) HashValue() (*big.Int, error) { b0 := big.NewInt(0) toHash := []*big.Int{b0, b0, b0, b0, b0, b0} lBI, err := a.BigInts() if err != nil { return nil, err } copy(toHash[:], lBI[:]) v, err := poseidon.Hash(toHash) return v, err } // AccountFromBigInts returns a Account from a [5]*big.Int func AccountFromBigInts(e [NLeafElems]*big.Int) (*Account, error) { if !cryptoUtils.CheckBigIntArrayInField(e[:]) { return nil, ErrNotInFF } var b [32 * NLeafElems]byte copy(b[0:32], SwapEndianness(e[0].Bytes())) // SwapEndianness, as big.Int uses BigEndian copy(b[32:64], SwapEndianness(e[1].Bytes())) copy(b[64:96], SwapEndianness(e[2].Bytes())) copy(b[96:128], SwapEndianness(e[3].Bytes())) return AccountFromBytes(b) } // AccountFromBytes returns a Account from a byte array func AccountFromBytes(b [32 * NLeafElems]byte) (*Account, error) { tokenID := binary.LittleEndian.Uint32(b[0:4]) var nonceBytes5 [5]byte copy(nonceBytes5[:], b[4:9]) nonce := NonceFromBytes(nonceBytes5) sign := b[10] == 1 balance := new(big.Int).SetBytes(SwapEndianness(b[32:56])) // b[32:56], as Balance is 192 bits (24 bytes) if !bytes.Equal(b[56:64], []byte{0, 0, 0, 0, 0, 0, 0, 0}) { return nil, fmt.Errorf("%s Balance", ErrNumOverflow) } ay := new(big.Int).SetBytes(SwapEndianness(b[64:96])) pkPoint, err := babyjub.PointFromSignAndY(sign, ay) if err != nil { return nil, err } publicKey := babyjub.PublicKey(*pkPoint) ethAddr := ethCommon.BytesToAddress(b[96:116]) if !cryptoUtils.CheckBigIntInField(balance) { return nil, ErrNotInFF } if !cryptoUtils.CheckBigIntInField(ay) { return nil, ErrNotInFF } a := Account{ TokenID: TokenID(tokenID), Nonce: nonce, Balance: balance, PublicKey: &publicKey, EthAddr: ethAddr, } return &a, nil }