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// Copyright (C) 2019-2023 Algorand, Inc.
// This file is part of go-algorand
//
// go-algorand is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as
// published by the Free Software Foundation, either version 3 of the
// License, or (at your option) any later version.
//
// go-algorand is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with go-algorand. If not, see <https://www.gnu.org/licenses/>.
package merklesignature
import (
"errors"
)
var errRoundFirstValid = errors.New("the round cannot be less than firstValid")
func checkMerkleSignatureSchemeParams(firstValid, round, keyLifetime uint64) error {
if keyLifetime == 0 {
return ErrKeyLifetimeIsZero
}
if round < firstValid {
return errRoundFirstValid
}
return nil
}
func roundToIndex(firstValid, currentRound, interval uint64) uint64 {
rofi := roundOfFirstIndex(firstValid, interval)
return (currentRound - rofi) / interval
}
func indexToRound(firstValid, interval, pos uint64) uint64 {
return roundOfFirstIndex(firstValid, interval) + pos*interval
}
func roundOfFirstIndex(firstValid, interval uint64) uint64 {
return ((firstValid + interval - 1) / interval) * interval
}
// firstRoundInKeyLifetime calculates the round of the valid key for a given round by lowering to the closest KeyLiftime divisor.
// It is implicitly assumed that round is larger than keyLifetime, as an MSS key for round 0 is not valid.
// A key lifetime of 0 is invalid.
func firstRoundInKeyLifetime(round, keyLifetime uint64) uint64 {
return round - (round % keyLifetime)
}
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