github.com/amazechain/amc@v0.1.3/common/crypto/bn256/cloudflare/gfp.go (about)

     1  // Copyright 2023 The AmazeChain Authors
     2  // This file is part of the AmazeChain library.
     3  //
     4  // The AmazeChain library is free software: you can redistribute it and/or modify
     5  // it under the terms of the GNU Lesser General Public License as published by
     6  // the Free Software Foundation, either version 3 of the License, or
     7  // (at your option) any later version.
     8  //
     9  // The AmazeChain library is distributed in the hope that it will be useful,
    10  // but WITHOUT ANY WARRANTY; without even the implied warranty of
    11  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    12  // GNU Lesser General Public License for more details.
    13  //
    14  // You should have received a copy of the GNU Lesser General Public License
    15  // along with the AmazeChain library. If not, see <http://www.gnu.org/licenses/>.
    16  
    17  package bn256
    18  
    19  import (
    20  	"errors"
    21  	"fmt"
    22  )
    23  
    24  type gfP [4]uint64
    25  
    26  func newGFp(x int64) (out *gfP) {
    27  	if x >= 0 {
    28  		out = &gfP{uint64(x)}
    29  	} else {
    30  		out = &gfP{uint64(-x)}
    31  		gfpNeg(out, out)
    32  	}
    33  
    34  	montEncode(out, out)
    35  	return out
    36  }
    37  
    38  func (e *gfP) String() string {
    39  	return fmt.Sprintf("%16.16x%16.16x%16.16x%16.16x", e[3], e[2], e[1], e[0])
    40  }
    41  
    42  func (e *gfP) Set(f *gfP) {
    43  	e[0] = f[0]
    44  	e[1] = f[1]
    45  	e[2] = f[2]
    46  	e[3] = f[3]
    47  }
    48  
    49  func (e *gfP) Invert(f *gfP) {
    50  	bits := [4]uint64{0x3c208c16d87cfd45, 0x97816a916871ca8d, 0xb85045b68181585d, 0x30644e72e131a029}
    51  
    52  	sum, power := &gfP{}, &gfP{}
    53  	sum.Set(rN1)
    54  	power.Set(f)
    55  
    56  	for word := 0; word < 4; word++ {
    57  		for bit := uint(0); bit < 64; bit++ {
    58  			if (bits[word]>>bit)&1 == 1 {
    59  				gfpMul(sum, sum, power)
    60  			}
    61  			gfpMul(power, power, power)
    62  		}
    63  	}
    64  
    65  	gfpMul(sum, sum, r3)
    66  	e.Set(sum)
    67  }
    68  
    69  func (e *gfP) Marshal(out []byte) {
    70  	for w := uint(0); w < 4; w++ {
    71  		for b := uint(0); b < 8; b++ {
    72  			out[8*w+b] = byte(e[3-w] >> (56 - 8*b))
    73  		}
    74  	}
    75  }
    76  
    77  func (e *gfP) Unmarshal(in []byte) error {
    78  	// Unmarshal the bytes into little endian form
    79  	for w := uint(0); w < 4; w++ {
    80  		for b := uint(0); b < 8; b++ {
    81  			e[3-w] += uint64(in[8*w+b]) << (56 - 8*b)
    82  		}
    83  	}
    84  	// Ensure the point respects the curve modulus
    85  	for i := 3; i >= 0; i-- {
    86  		if e[i] < p2[i] {
    87  			return nil
    88  		}
    89  		if e[i] > p2[i] {
    90  			return errors.New("bn256: coordinate exceeds modulus")
    91  		}
    92  	}
    93  	return errors.New("bn256: coordinate equals modulus")
    94  }
    95  
    96  func montEncode(c, a *gfP) { gfpMul(c, a, r2) }
    97  func montDecode(c, a *gfP) { gfpMul(c, a, &gfP{1}) }