package crypto

import (
    "bytes"
    "crypto/sha256"
)

func SignData(data []byte, secretKey [32]byte) []byte {
    h := sha256.New()
    h.Write(data)
    h.Write(secretKey[:])
    return h.Sum(data)
}

func VerifySignature(data []byte, secretKey [32]byte) bool {
    dgLen := len(data)
    unsignedLen := dgLen-32
    signature := data[unsignedLen:]

    tmp := make([]byte, len(data))
    copy(tmp, data[:unsignedLen])
    copy(tmp[unsignedLen:], secretKey[:])

    computed := sha256.Sum256(tmp)

    return bytes.Equal(signature, computed[:])
}