1// Copyright (C) 2019 ProtonTech AG
 2
 3package algorithm
 4
 5import (
 6	"crypto/cipher"
 7	"github.com/ProtonMail/go-crypto/eax"
 8	"github.com/ProtonMail/go-crypto/ocb"
 9)
10
11// AEADMode defines the Authenticated Encryption with Associated Data mode of
12// operation.
13type AEADMode uint8
14
15// Supported modes of operation (see RFC4880bis [EAX] and RFC7253)
16const (
17	AEADModeEAX = AEADMode(1)
18	AEADModeOCB = AEADMode(2)
19	AEADModeGCM = AEADMode(3)
20)
21
22// TagLength returns the length in bytes of authentication tags.
23func (mode AEADMode) TagLength() int {
24	switch mode {
25	case AEADModeEAX:
26		return 16
27	case AEADModeOCB:
28		return 16
29	case AEADModeGCM:
30		return 16
31	default:
32		return 0
33	}
34}
35
36// NonceLength returns the length in bytes of nonces.
37func (mode AEADMode) NonceLength() int {
38	switch mode {
39	case AEADModeEAX:
40		return 16
41	case AEADModeOCB:
42		return 15
43	case AEADModeGCM:
44		return 12
45	default:
46		return 0
47	}
48}
49
50// New returns a fresh instance of the given mode
51func (mode AEADMode) New(block cipher.Block) (alg cipher.AEAD) {
52	var err error
53	switch mode {
54	case AEADModeEAX:
55		alg, err = eax.NewEAX(block)
56	case AEADModeOCB:
57		alg, err = ocb.NewOCB(block)
58	case AEADModeGCM:
59		alg, err = cipher.NewGCM(block)
60	}
61	if err != nil {
62		panic(err.Error())
63	}
64	return alg
65}