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package integergroup
import (
"crypto/rand"
"crypto/sha256"
"fmt"
"golang.org/x/crypto/hkdf"
"io"
"math/big"
)
func expandArbitraryElementSeed(data []byte, numbytes int) ([]byte, error) {
info := []byte("SPAKE2 arbitrary element")
hkdfReader := hkdf.New(sha256.New, data, []byte(""), info)
expandedData := make([]byte, numbytes)
n, err := io.ReadFull(hkdfReader, expandedData)
if err != nil {
return nil, err
}
if n != numbytes {
return nil, fmt.Errorf(
"Failed to read %d bytes, only read: %d bytes", numbytes, n)
}
return expandedData, nil
}
func unbiasedRandRange(start, stop *big.Int) (*big.Int, error) {
var maxVal big.Int
maxVal.Sub(stop, start)
return rand.Int(rand.Reader, &maxVal)
}
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