51 lines
1.9 KiB
Go
51 lines
1.9 KiB
Go
package multiexp
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import (
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"github.com/consensys/gnark-crypto/ecc"
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bls12381 "github.com/consensys/gnark-crypto/ecc/bls12-381"
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"github.com/consensys/gnark-crypto/ecc/bls12-381/fr"
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)
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// MultiExpG1 computes a multi exponentiation -- That is, an inner product between points and scalars.
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//
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// More precisely, the result is set to scalars[0]*points[0] + ... + scalars[n-1]*points[n-1], where n is the length of both slices
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// If the slices differ in length, this function returns an error.
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//
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// numGoRoutines is used to configure the amount of concurrency needed. Setting this
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// value to a negative number or 0 will make it default to the number of CPUs.
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//
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// Returns an error if the numGoRoutines exceeds 1024.
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//
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// [g1_lincomb]: https://github.com/ethereum/consensus-specs/blob/017a8495f7671f5fff2075a9bfc9238c1a0982f8/specs/deneb/polynomial-commitments.md#g1_lincomb
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func MultiExpG1(scalars []fr.Element, points []bls12381.G1Affine, numGoRoutines int) (*bls12381.G1Affine, error) {
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err := isValidNumGoRoutines(numGoRoutines)
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if err != nil {
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return nil, err
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}
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return new(bls12381.G1Affine).MultiExp(points, scalars, ecc.MultiExpConfig{NbTasks: numGoRoutines})
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}
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func MultiExpG2(scalars []fr.Element, points []bls12381.G2Affine, numGoRoutines int) (*bls12381.G2Affine, error) {
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err := isValidNumGoRoutines(numGoRoutines)
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if err != nil {
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return nil, err
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}
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return new(bls12381.G2Affine).MultiExp(points, scalars, ecc.MultiExpConfig{NbTasks: numGoRoutines})
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}
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// isValidNumGoRoutines will return an error if the number
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// of go routines to be used is not Valid.
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//
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// Valid meaning that is less than 1024.
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//
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// 1024 is chosen here as the underlying gnark-crypto library will
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// return an error for more than 1024.
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// Instead of waiting until the user tries to call an algorithm
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// which requires numGoRoutines, we return the error here instead.
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func isValidNumGoRoutines(value int) error {
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if value >= 1024 {
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return ErrTooManyGoRoutines
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}
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return nil
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}
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