31 lines
1.1 KiB
Go
31 lines
1.1 KiB
Go
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// Copyright (c) 2016 Andreas Auernhammer. All rights reserved.
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// Use of this source code is governed by a license that can be
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// found in the LICENSE file.
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// Package poly1305 implements Poly1305 one-time message authentication code
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// defined in RFC 7539..
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//
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// Poly1305 is a fast, one-time authentication function. It is infeasible for an
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// attacker to generate an authenticator for a message without the key.
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// However, a key must only be used for a single message. Authenticating two
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// different messages with the same key allows an attacker to forge
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// authenticators for other messages with the same key.
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package poly1305 // import "github.com/aead/poly1305"
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import (
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"crypto/subtle"
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"errors"
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)
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// TagSize is the size of the poly1305 authentication tag in bytes.
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const TagSize = 16
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var errWriteAfterSum = errors.New("checksum already computed - adding more data is not allowed")
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// Verify returns true if and only if the mac is a valid authenticator
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// for msg with the given key.
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func Verify(mac *[TagSize]byte, msg []byte, key [32]byte) bool {
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sum := Sum(msg, key)
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return subtle.ConstantTimeCompare(sum[:], mac[:]) == 1
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}
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