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// Copyright (C) 2019 ProtonTech AG
package algorithm
import (
"crypto/cipher"
"github.com/ProtonMail/go-crypto/eax"
"github.com/ProtonMail/go-crypto/ocb"
)
// AEADMode defines the Authenticated Encryption with Associated Data mode of
// operation.
type AEADMode uint8
// Supported modes of operation (see RFC4880bis [EAX] and RFC7253)
const (
AEADModeEAX = AEADMode(1)
AEADModeOCB = AEADMode(2)
AEADModeGCM = AEADMode(3)
)
// TagLength returns the length in bytes of authentication tags.
func (mode AEADMode) TagLength() int {
switch mode {
case AEADModeEAX:
return 16
case AEADModeOCB:
return 16
case AEADModeGCM:
return 16
default:
return 0
}
}
// NonceLength returns the length in bytes of nonces.
func (mode AEADMode) NonceLength() int {
switch mode {
case AEADModeEAX:
return 16
case AEADModeOCB:
return 15
case AEADModeGCM:
return 12
default:
return 0
}
}
// New returns a fresh instance of the given mode
func (mode AEADMode) New(block cipher.Block) (alg cipher.AEAD) {
var err error
switch mode {
case AEADModeEAX:
alg, err = eax.NewEAX(block)
case AEADModeOCB:
alg, err = ocb.NewOCB(block)
case AEADModeGCM:
alg, err = cipher.NewGCM(block)
}
if err != nil {
panic(err.Error())
}
return alg
}
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