2 GoVPN -- simple secure free software virtual private network daemon
3 Copyright (C) 2014-2016 Sergey Matveev <stargrave@stargrave.org>
5 This program is free software: you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation, either version 3 of the License, or
8 (at your option) any later version.
10 This program is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
15 You should have received a copy of the GNU General Public License
16 along with this program. If not, see <http://www.gnu.org/licenses/>.
24 "github.com/pkg/errors"
26 "cypherpunks.ru/govpn/aont"
27 "cypherpunks.ru/govpn/cnw"
30 // EnclessEnlargeSize is number of bytes overhead for each message
31 const EnclessEnlargeSize = aont.HSize + aont.RSize*cnw.EnlargeFactor
33 // EnclessEncode is encryptionless, but confidentiality preserving encoding.
35 // It uses Chaffing-and-Winnowing technology (it is neither
36 // encryption nor steganography) over All-Or-Nothing-Transformed data.
37 // nonce is 64-bit nonce. Output data will be EnclessEnlargeSize larger.
38 // It also consumes 64-bits of entropy.
39 func EnclessEncode(authKey *[32]byte, nonce *[16]byte, in []byte) ([]byte, error) {
40 r := new([aont.RSize]byte)
42 if _, err = io.ReadFull(Rand, r[:]); err != nil {
43 return nil, errors.Wrapf(err, wrapIoReadFull, "Rand")
45 aonted, err := aont.Encode(r, in)
47 return nil, errors.Wrap(err, "aont.Encode")
50 cnw.Chaff(authKey, nonce[8:], aonted[:aont.RSize]),
51 aonted[aont.RSize:]...,
53 SliceZero(aonted[:aont.RSize])
57 // EnclessDecode decodes EnclessEncode-ed data.
58 func EnclessDecode(authKey *[32]byte, nonce *[16]byte, in []byte) ([]byte, error) {
60 winnowed, err := cnw.Winnow(
61 authKey, nonce[8:], in[:aont.RSize*cnw.EnlargeFactor],
64 return nil, errors.Wrap(err, "cnw.Winnow")
66 out, err := aont.Decode(append(
67 winnowed, in[aont.RSize*cnw.EnlargeFactor:]...,
71 return nil, errors.Wrap(err, "aont.Decode")