github.com/snowblossomcoin/go-ethereum@v1.9.25/crypto/bls12381/gt.go (about)

     1  // Copyright 2020 The go-ethereum Authors
     2  // This file is part of the go-ethereum library.
     3  //
     4  // The go-ethereum 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 go-ethereum 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 go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
    16  
    17  package bls12381
    18  
    19  import (
    20  	"errors"
    21  	"math/big"
    22  )
    23  
    24  // E is type for target group element
    25  type E = fe12
    26  
    27  // GT is type for target multiplicative group GT.
    28  type GT struct {
    29  	fp12 *fp12
    30  }
    31  
    32  func (e *E) Set(e2 *E) *E {
    33  	return e.set(e2)
    34  }
    35  
    36  // One sets a new target group element to one
    37  func (e *E) One() *E {
    38  	e = new(fe12).one()
    39  	return e
    40  }
    41  
    42  // IsOne returns true if given element equals to one
    43  func (e *E) IsOne() bool {
    44  	return e.isOne()
    45  }
    46  
    47  // Equal returns true if given two element is equal, otherwise returns false
    48  func (g *E) Equal(g2 *E) bool {
    49  	return g.equal(g2)
    50  }
    51  
    52  // NewGT constructs new target group instance.
    53  func NewGT() *GT {
    54  	fp12 := newFp12(nil)
    55  	return &GT{fp12}
    56  }
    57  
    58  // Q returns group order in big.Int.
    59  func (g *GT) Q() *big.Int {
    60  	return new(big.Int).Set(q)
    61  }
    62  
    63  // FromBytes expects 576 byte input and returns target group element
    64  // FromBytes returns error if given element is not on correct subgroup.
    65  func (g *GT) FromBytes(in []byte) (*E, error) {
    66  	e, err := g.fp12.fromBytes(in)
    67  	if err != nil {
    68  		return nil, err
    69  	}
    70  	if !g.IsValid(e) {
    71  		return e, errors.New("invalid element")
    72  	}
    73  	return e, nil
    74  }
    75  
    76  // ToBytes serializes target group element.
    77  func (g *GT) ToBytes(e *E) []byte {
    78  	return g.fp12.toBytes(e)
    79  }
    80  
    81  // IsValid checks whether given target group element is in correct subgroup.
    82  func (g *GT) IsValid(e *E) bool {
    83  	r := g.New()
    84  	g.fp12.exp(r, e, q)
    85  	return r.isOne()
    86  }
    87  
    88  // New initializes a new target group element which is equal to one
    89  func (g *GT) New() *E {
    90  	return new(E).One()
    91  }
    92  
    93  // Add adds two field element `a` and `b` and assigns the result to the element in first argument.
    94  func (g *GT) Add(c, a, b *E) {
    95  	g.fp12.add(c, a, b)
    96  }
    97  
    98  // Sub subtracts two field element `a` and `b`, and assigns the result to the element in first argument.
    99  func (g *GT) Sub(c, a, b *E) {
   100  	g.fp12.sub(c, a, b)
   101  }
   102  
   103  // Mul multiplies two field element `a` and `b` and assigns the result to the element in first argument.
   104  func (g *GT) Mul(c, a, b *E) {
   105  	g.fp12.mul(c, a, b)
   106  }
   107  
   108  // Square squares an element `a` and assigns the result to the element in first argument.
   109  func (g *GT) Square(c, a *E) {
   110  	g.fp12.cyclotomicSquare(c, a)
   111  }
   112  
   113  // Exp exponents an element `a` by a scalar `s` and assigns the result to the element in first argument.
   114  func (g *GT) Exp(c, a *E, s *big.Int) {
   115  	g.fp12.cyclotomicExp(c, a, s)
   116  }
   117  
   118  // Inverse inverses an element `a` and assigns the result to the element in first argument.
   119  func (g *GT) Inverse(c, a *E) {
   120  	g.fp12.inverse(c, a)
   121  }