ceremonyclient/nekryptology/pkg/accumulator/lib.go
2023-07-05 00:32:28 -05:00

205 lines
4.3 KiB
Go

//
// Copyright Coinbase, Inc. All Rights Reserved.
//
// SPDX-License-Identifier: Apache-2.0
//
package accumulator
import (
"fmt"
"math"
"source.quilibrium.com/quilibrium/monorepo/nekryptology/pkg/core/curves"
)
// dad constructs two polynomials - dA(x) and dD(x)
// dA(y) = prod(y_A,t - y), t = 1...n
// dD(y) = prod(y_D,t - y), t = 1...n
func dad(values []Element, y Element) (Element, error) {
if values == nil || y == nil {
return nil, fmt.Errorf("curve, values or y should not be nil")
}
for _, value := range values {
if value == nil {
return nil, fmt.Errorf("some element is nil")
}
}
result := y.One()
if len(values) == 1 {
a := values[0]
result = a.Sub(y)
} else {
for i := 0; i < len(values); i++ {
temp := values[i].Sub(y)
result = result.Mul(temp)
}
}
return result, nil
}
type polynomialPoint []curves.Point
// evaluate evaluates a PolynomialG1 on input x.
func (p polynomialPoint) evaluate(x curves.Scalar) (curves.Point, error) {
if p == nil {
return nil, fmt.Errorf("p cannot be empty")
}
for i := 0; i < len(p); i++ {
if p[i] == nil {
return nil, fmt.Errorf("some coefficient in p is nil")
}
}
pp := x
res := p[0]
for i := 1; i < len(p); i++ {
r := p[i].Mul(pp)
res = res.Add(r)
pp = pp.Mul(x)
}
return res, nil
}
// Add adds two PolynomialG1
func (p polynomialPoint) Add(rhs polynomialPoint) (polynomialPoint, error) {
maxLen := int(math.Max(float64(len(p)), float64(len(rhs))))
result := make(polynomialPoint, maxLen)
for i, c := range p {
if c == nil {
return nil, fmt.Errorf("invalid coefficient at %d", i)
}
result[i] = c.Add(c.Identity())
}
for i, c := range rhs {
if c == nil {
return nil, fmt.Errorf("invalid coefficient at %d", i)
}
if result[i] == nil {
result[i] = c.Add(c.Identity())
} else {
result[i] = result[i].Add(c)
}
}
return result, nil
}
// Mul for PolynomialG1 computes rhs * p, p is a polynomial, rhs is a value
func (p polynomialPoint) Mul(rhs curves.Scalar) (polynomialPoint, error) {
result := make(polynomialPoint, len(p))
for i, c := range p {
if c == nil {
return nil, fmt.Errorf("invalid coefficient at %d", i)
}
result[i] = c.Mul(rhs)
}
return result, nil
}
type polynomial []curves.Scalar
// Add adds two polynomials
func (p polynomial) Add(rhs polynomial) (polynomial, error) {
maxLen := int(math.Max(float64(len(p)), float64(len(rhs))))
result := make([]curves.Scalar, maxLen)
for i, c := range p {
if c == nil {
return nil, fmt.Errorf("invalid coefficient at %d", i)
}
result[i] = c.Clone()
}
for i, c := range rhs {
if c == nil {
return nil, fmt.Errorf("invalid coefficient at %d", i)
}
if result[i] == nil {
result[i] = c.Clone()
} else {
result[i] = result[i].Add(c)
}
}
return result, nil
}
// Sub computes p-rhs and returns
func (p polynomial) Sub(rhs polynomial) (polynomial, error) {
maxLen := int(math.Max(float64(len(p)), float64(len(rhs))))
result := make([]curves.Scalar, maxLen)
for i, c := range p {
if c == nil {
return nil, fmt.Errorf("invalid coefficient at %d", i)
}
result[i] = c.Clone()
}
for i, c := range rhs {
if c == nil {
return nil, fmt.Errorf("invalid coefficient at %d", i)
}
if result[i] == nil {
result[i] = c.Neg()
} else {
result[i] = result[i].Sub(c)
}
}
return result, nil
}
// Mul multiplies two polynomials - p * rhs
func (p polynomial) Mul(rhs polynomial) (polynomial, error) {
// Check for each coefficient that should not be nil
for i, c := range p {
if c == nil {
return nil, fmt.Errorf("coefficient in p at %d is nil", i)
}
}
for i, c := range rhs {
if c == nil {
return nil, fmt.Errorf("coefficient in rhs at %d is nil", i)
}
}
m := len(p)
n := len(rhs)
// Initialize the product polynomial
prod := make(polynomial, m+n-1)
for i := 0; i < len(prod); i++ {
prod[i] = p[0].Zero()
}
// Multiply two polynomials term by term
for i, cp := range p {
for j, cr := range rhs {
temp := cp.Mul(cr)
prod[i+j] = prod[i+j].Add(temp)
}
}
return prod, nil
}
// MulScalar computes p * rhs, where rhs is a scalar value
func (p polynomial) MulScalar(rhs curves.Scalar) (polynomial, error) {
result := make(polynomial, len(p))
for i, c := range p {
if c == nil {
return nil, fmt.Errorf("coefficient at %d is nil", i)
}
result[i] = c.Mul(rhs)
}
return result, nil
}