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INTERNET-DRAFT K.Kaukonen
14 July 1999 R.Thayer
Expires: 17 December 1999 SSH
A Stream Cipher Encryption Algorithm "Arcfour"
Status of this Memo
This document is an Internet-Draft and is in full conformance
with all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet
Engineering Task Force (IETF), its areas, and its working
groups. Note that other groups may also distribute working
documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use
Internet-Drafts as reference material or to cite them other
than as "work in progress."
The list of current Internet-Drafts can be accessed at
https://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
https://www.ietf.org/shadow.html.
Abstract
This document describes an algorithm here called Arcfour that is
believed to be fully interoperable with the RC4 algoritm. RC4
is trademark of RSA Data Security, Inc. There is a need in the
Internet community for an encryption algorithm that provides
interoperable operation with existing deployed commercial
cryptographic applications. This interoperability will allow
for a smoother transition to protocols that have been developed
through the IETF standards process.
Kaukonen,Thayer Page [1]
Internet Draft ARCFOUR Algorithm July, 1999
Contents
Status of this Memo . . . . . . . . . . . . . . . . . . . . 1
Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1. Introduction . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements for this Encryption Algorithm . . . . . . . 3
3. Description of Algorithm . . . . . . . . . . . . . . . . 3
3.1 Key Setup . . . . . . . . . . . . . . . . . . . . . . . 3
3.2 Stream Generation . . . . . . . . . . . . . . . . . . . 4
4. Intellectual Property Considerations . . . . . . . . . . 4
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . 5
7. References . . . . . . . . . . . . . . . . . . . . . . . 5
8. Colophon . . . . . . . . . . . . . . . . . . . . . . . . 6
8.1 Authors' Addresses . . . . . . . . . . . . . . . . . . . 6
8.2 About this document . . . . . . . . . . . . . . . . . . 6
8.3 Change History . . . . . . . . . . . . . . . . . . . . . 7
Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . 8
A. Test Vectors . . . . . . . . . . . . . . . . . . . . . . 8
B. Sample Code . . . . . . . . . . . . . . . . . . . . . . . 11
C. Copyright Statement . . . . . . . . . . . . . . . . . . . 14
Kaukonen,Thayer Page [2]
Internet Draft ARCFOUR Algorithm July, 1999
1. Introduction
There is a need in the Internet community for an encryption algorithm
that provides interoperable operation with existing deployed
commercial cryptographic applications. This interoperability allows
for a smoother transition to protocols that have been developed
through the IETF standards process. This document describes an
existing algorithm that satisifies this requirement.
There is a large body of experience in developing and deploying
encryption applications, especially in the HTTP/HTML browser/server
markets. These browsers typically implement the RC4 encryption
algorithm provided by [RSA]. It would be beneficial for the IETF
standards processes to produce protocols that can be deployed into
existing Internet environments. This would allow graceful addition
of new (IETF-developed) protocols. It would allow less disruption of
existing users, since there would be more interoperability between
pre-exisiting protocols and IETF-based protocols.
2. Requirements for this Encryption Algorithm
The algorithm described here is called Arcfour, and it has been
chosen because it is compatible with the RC4(TM) algorithm that is
one of the most popular encryption algorithms in the browser market.
(See chapter Intellectual Property Considerations.) Arcfour is
potentially useful in several environments, including IPSEC [IPSEC],
SSH [SSH], and TLS [TLS]. There are existing Internet Drafts that
describe how it can be applied, see e.g. [Caronni], [SSH], and [TLS].
The algorithm can be used with a variety of key lengths. It
specifically can be operated with 40-bit keys and with 128-bit keys.
See the Security Considerations section for comments on the use of
40-bit keys.
Compatibility of the algorithm with commercial algorithms can be
tested by comparing the encrypted data that is produced by the test
vectors listed in the appendix to this document.
3. Description of Algorithm
The algorithm itself is documented in [Schneier], pages 397-398, in
the chapter titled "Other Stream Ciphers and Real Random Sequence
Generators".
3.1 Key Setup
1. Allocate an 256 element array of 8 bit bytes to be used as an
S-box, label it
S [0] .. S [255].
2. Initialize the S-box. Fill each entry first with it's index:
S [0] = 0; S [1] = 1; etc. up to S [255] = 255;
Kaukonen,Thayer Page [3]
Internet Draft ARCFOUR Algorithm July, 1999
3. Fill another array of the same size (256) with the key, repeating
bytes as necessary.
for (i = 0; i < 256; i = i + 1)
S2 [i] = key [i % keylen];
4. Set j to zero and initialize the S-box like this:
for (i = 0; i < 256; i = i + 1)
{
j = (j + S [i] + S2 [i]) % 256;
temp = S [i];
S [i] = S [j];
S [j] = temp;
}
5. Initialize i and j to zero. If superuser priviledged program
sniffing is feared (that is, always) set also the S2 array and the
key array to zero. That gives a slightly better protection since
the key is believed to be not feasible to calculate after it has
been zeroed and thus forgotten.
3.2 Stream Generation
For either encryption or decryption, the input text is processed one
byte at a time. A pseudorandom byte K is generated:
i = (i+1) % 256;
j = (j + S[i]) % 256;
temp = S [i];
S [i] = S [j];
S [j] = temp;
t = (S [i] + S [j]) % 256;
K = S [t];
To encrypt, XOR the value K with the next byte of the plaintext. To
decrypt, XOR the value K with the next byte of the ciphertext.
4. Intellectual Property Considerations
This document does not address Intellectual Property issues. No claim
is made as to who owns this algorithm, of the performance of the
algorithm, its cryptographic security or any other liability issues
related to the algoritm itself, its implementation or use.
The Arcfour algorithm is believed to be fully interoperable with the
RC4 algorithm. "RC4" is believed to be trademark of RSA Data
Security, Inc. Contact [RSA] if RC4(TM) algorithm is needed.
5. Acknowledgements
This work was based on conversations with several collegues within
the IETF.
Kaukonen,Thayer Page [4]
Internet Draft ARCFOUR Algorithm July, 1999
6. Security Considerations
This algorithm can be operated with several different key sizes. If
the key is 128 bits in length then this algorithm is believed to be
secure. If the key length is significantly shorter, specifically 40
bits, then there are known attacts that have been successfully
applied. For this algorithm to be operated in a cryptographically
sound manner it is believed that a key length of 128 bits or more
should be used.
On the other hand, the 40-bit version of this algorithm is
specifically regulated by the U.S. Government. This means that
deployment of 40-bit implementations may be easier to export than
alternative algorithms.
It must be strongly recommended that no two plaintexts are encrypted
with the same key. Otherwise the plaintext can usually be broken, and
often even quite easily. If the two encrypted messages are XORed
together, the result is the XOR of the original plaintexts. Given the
encrypted messages are text strings, credit card numbers, or other
byte streams with some known properties, the plaintexts can be
estimated with great accuracy. See the [DAWSON AND NIELSEN] for more
details.
Initial cryptanalysis results are favorable, but the current
literature should be consulted to assess the security of this cipher.
A good starting point for a citation search would be [GOLIC]. For
Internet news group posting, start with [FINNEY], [JENKINS] and
[ROOS].
7. References
[Caronni] Caronni, G., Waldvogel, M. "The ESP Stream Transform",
ftp://ds.internic.net/internet-drafts/
draft-caronni-esp-stream-01.txt, September, 1996.
[COMMERCE] Test vectors issued by United States Department of
Commerce, Bureau of Export Administration, Office of Strategic
Trade and Foreign Policy, Strategic Trade Controls Division.
[CRYPTLIB] Gutmann, P, Young, E., Plumb, C. "Cryptlib, A Portable
Encryption Library", Version 2.00.
https://www.cs.auckland.ac.nz/~pgut001/cryptlib.html, 1996.
[DAWSON AND NIELSEN] Dawson E. and Nielsen L.: Automated
Cryptoanalysis of XOR Plaintext Strings, Cryptologia, April 1996,
Volume XX, Number 2.
[FINNEY] Finney, H. Internet message posted to sci.crypt 21
September, 1994.
[GOLIC] Golic, J. "Linear Statistical Weakness of Alleged RC4
Keystream Generator." In, W. Fumy (ed.), Proceedings of Eurocrypt
Kaukonen,Thayer Page [5]
Internet Draft ARCFOUR Algorithm July, 1999
'97, 226-238, Springer-Verlag, 1997.
[IPSEC] Atkinson, R, "Security Architecture for the Internet
Protocol", ftp://ds.internic.net/rfc/rfc1825.txt, August 1995.
[JENKINS] Jenkins, B. Internet message posted to sci.crypt 22
September, 1994.
[ROOS] Roos, A. Internet message posted to sci.crypt 28 September,
1995.
[RSA] RSA Data Security, Inc., https://www.rsa.com, Address: RSA Data
Security, Inc. 100 Marine Parkway, Suite 500, Redwood City, CA
94065-1031.
[SCHNEIER] Schneier, B. "Applied Cryptography", Second Edition,
https://www.counterpane.com. Published by John Wiley & Sons, Inc.
ISBN 0-471-11709-9, 1996.
[SSH] Ylonen, T., "SSH Transport Layer Protocol",
ftp://ietf.org/internet-drafts/draft-ietf-secsh-transport-00.txt,
March, 1997.
[SSH ARCFOUR] Kaukonen, K. Long test vectors for Arcfour and RC4
algorithms issued by Kalle Kaukonen, SSH Communications Security, Ltd,
July, 1997.
[TLS] Freier, A., Karlton, P., Kocher, P., Dierks, T., "The TLS
Protocol", ftp://ds.internic.net/internet-drafts/
draft-ietf-tls-protocol-00.txt, December, 1996.
8. Colophon
8.1 Authors' Addresses
Kalle Kaukonen
SSH Communications Security Oy
Tekniikantie 12
02150 Espoo
Finland
kalle@ssh.fi
https://www.ssh.fi
Rodney Thayer
SSH Communications Security, Inc.
650 Castro Street, Suite 220
Mountain View, CA 94041
rodney@ipsec.com
8.2 About this document
This document was written in plain text using 'ifmt', a text formatter
designed to work on generic C platforms. Original source is in
plain ascii, transliterated from the original NROFF source.
Kaukonen,Thayer Page [6]
Internet Draft ARCFOUR Algorithm July, 1999
IETF draft boilerplate was current at the time this document was
published.
8.3 Change History
This is revision 02 of draft-kaukonen-cipher-arcfour. This revision
is a resubmission only.
Kaukonen,Thayer Page [7]
Internet Draft ARCFOUR Algorithm July, 1999
Appendix
A. Test Vectors
1. Test Vectors from [CRYPTLIB]:
Plain Text:
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
Key:
0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF
Cipher Text:
0x74, 0x94, 0xC2, 0xE7, 0x10, 0x4B, 0x08, 0x79
2. Test Vectors from [COMMERCE]:
Plain Text:
0xdc, 0xee, 0x4c, 0xf9, 0x2c
Key:
0x61, 0x8a, 0x63, 0xd2, 0xfb
Cipher Text:
0xf1, 0x38, 0x29, 0xc9, 0xde
3. Test Vectors from [SSH ARCFOUR]:
Plain Text:
0x52, 0x75, 0x69, 0x73, 0x6c, 0x69, 0x6e, 0x6e,
0x75, 0x6e, 0x20, 0x6c, 0x61, 0x75, 0x6c, 0x75,
0x20, 0x6b, 0x6f, 0x72, 0x76, 0x69, 0x73, 0x73,
0x73, 0x61, 0x6e, 0x69, 0x2c, 0x20, 0x74, 0xe4,
0x68, 0x6b, 0xe4, 0x70, 0xe4, 0x69, 0x64, 0x65,
0x6e, 0x20, 0x70, 0xe4, 0xe4, 0x6c, 0x6c, 0xe4,
0x20, 0x74, 0xe4, 0x79, 0x73, 0x69, 0x6b, 0x75,
0x75, 0x2e, 0x20, 0x4b, 0x65, 0x73, 0xe4, 0x79,
0xf6, 0x6e, 0x20, 0x6f, 0x6e, 0x20, 0x6f, 0x6e,
0x6e, 0x69, 0x20, 0x6f, 0x6d, 0x61, 0x6e, 0x61,
0x6e, 0x69, 0x2c, 0x20, 0x6b, 0x61, 0x73, 0x6b,
0x69, 0x73, 0x61, 0x76, 0x75, 0x75, 0x6e, 0x20,
0x6c, 0x61, 0x61, 0x6b, 0x73, 0x6f, 0x74, 0x20,
0x76, 0x65, 0x72, 0x68, 0x6f, 0x75, 0x75, 0x2e,
0x20, 0x45, 0x6e, 0x20, 0x6d, 0x61, 0x20, 0x69,
0x6c, 0x6f, 0x69, 0x74, 0x73, 0x65, 0x2c, 0x20,
0x73, 0x75, 0x72, 0x65, 0x20, 0x68, 0x75, 0x6f,
0x6b, 0x61, 0x61, 0x2c, 0x20, 0x6d, 0x75, 0x74,
0x74, 0x61, 0x20, 0x6d, 0x65, 0x74, 0x73, 0xe4,
0x6e, 0x20, 0x74, 0x75, 0x6d, 0x6d, 0x75, 0x75,
0x73, 0x20, 0x6d, 0x75, 0x6c, 0x6c, 0x65, 0x20,
0x74, 0x75, 0x6f, 0x6b, 0x61, 0x61, 0x2e, 0x20,
0x50, 0x75, 0x75, 0x6e, 0x74, 0x6f, 0x20, 0x70,
0x69, 0x6c, 0x76, 0x65, 0x6e, 0x2c, 0x20, 0x6d,
0x69, 0x20, 0x68, 0x75, 0x6b, 0x6b, 0x75, 0x75,
0x2c, 0x20, 0x73, 0x69, 0x69, 0x6e, 0x74, 0x6f,
0x20, 0x76, 0x61, 0x72, 0x61, 0x6e, 0x20, 0x74,
0x75, 0x75, 0x6c, 0x69, 0x73, 0x65, 0x6e, 0x2c,
Kaukonen,Thayer Page [8]
Internet Draft ARCFOUR Algorithm July, 1999
0x20, 0x6d, 0x69, 0x20, 0x6e, 0x75, 0x6b, 0x6b,
0x75, 0x75, 0x2e, 0x20, 0x54, 0x75, 0x6f, 0x6b,
0x73, 0x75, 0x74, 0x20, 0x76, 0x61, 0x6e, 0x61,
0x6d, 0x6f, 0x6e, 0x20, 0x6a, 0x61, 0x20, 0x76,
0x61, 0x72, 0x6a, 0x6f, 0x74, 0x20, 0x76, 0x65,
0x65, 0x6e, 0x2c, 0x20, 0x6e, 0x69, 0x69, 0x73,
0x74, 0xe4, 0x20, 0x73, 0x79, 0x64, 0xe4, 0x6d,
0x65, 0x6e, 0x69, 0x20, 0x6c, 0x61, 0x75, 0x6c,
0x75, 0x6e, 0x20, 0x74, 0x65, 0x65, 0x6e, 0x2e,
0x20, 0x2d, 0x20, 0x45, 0x69, 0x6e, 0x6f, 0x20,
0x4c, 0x65, 0x69, 0x6e, 0x6f
Key:
0x29, 0x04, 0x19, 0x72, 0xfb, 0x42, 0xba, 0x5f,
0xc7, 0x12, 0x77, 0x12, 0xf1, 0x38, 0x29, 0xc9
Cipher Text:
0x35, 0x81, 0x86, 0x99, 0x90, 0x01, 0xe6, 0xb5,
0xda, 0xf0, 0x5e, 0xce, 0xeb, 0x7e, 0xee, 0x21,
0xe0, 0x68, 0x9c, 0x1f, 0x00, 0xee, 0xa8, 0x1f,
0x7d, 0xd2, 0xca, 0xae, 0xe1, 0xd2, 0x76, 0x3e,
0x68, 0xaf, 0x0e, 0xad, 0x33, 0xd6, 0x6c, 0x26,
0x8b, 0xc9, 0x46, 0xc4, 0x84, 0xfb, 0xe9, 0x4c,
0x5f, 0x5e, 0x0b, 0x86, 0xa5, 0x92, 0x79, 0xe4,
0xf8, 0x24, 0xe7, 0xa6, 0x40, 0xbd, 0x22, 0x32,
0x10, 0xb0, 0xa6, 0x11, 0x60, 0xb7, 0xbc, 0xe9,
0x86, 0xea, 0x65, 0x68, 0x80, 0x03, 0x59, 0x6b,
0x63, 0x0a, 0x6b, 0x90, 0xf8, 0xe0, 0xca, 0xf6,
0x91, 0x2a, 0x98, 0xeb, 0x87, 0x21, 0x76, 0xe8,
0x3c, 0x20, 0x2c, 0xaa, 0x64, 0x16, 0x6d, 0x2c,
0xce, 0x57, 0xff, 0x1b, 0xca, 0x57, 0xb2, 0x13,
0xf0, 0xed, 0x1a, 0xa7, 0x2f, 0xb8, 0xea, 0x52,
0xb0, 0xbe, 0x01, 0xcd, 0x1e, 0x41, 0x28, 0x67,
0x72, 0x0b, 0x32, 0x6e, 0xb3, 0x89, 0xd0, 0x11,
0xbd, 0x70, 0xd8, 0xaf, 0x03, 0x5f, 0xb0, 0xd8,
0x58, 0x9d, 0xbc, 0xe3, 0xc6, 0x66, 0xf5, 0xea,
0x8d, 0x4c, 0x79, 0x54, 0xc5, 0x0c, 0x3f, 0x34,
0x0b, 0x04, 0x67, 0xf8, 0x1b, 0x42, 0x59, 0x61,
0xc1, 0x18, 0x43, 0x07, 0x4d, 0xf6, 0x20, 0xf2,
0x08, 0x40, 0x4b, 0x39, 0x4c, 0xf9, 0xd3, 0x7f,
0xf5, 0x4b, 0x5f, 0x1a, 0xd8, 0xf6, 0xea, 0x7d,
0xa3, 0xc5, 0x61, 0xdf, 0xa7, 0x28, 0x1f, 0x96,
0x44, 0x63, 0xd2, 0xcc, 0x35, 0xa4, 0xd1, 0xb0,
0x34, 0x90, 0xde, 0xc5, 0x1b, 0x07, 0x11, 0xfb,
0xd6, 0xf5, 0x5f, 0x79, 0x23, 0x4d, 0x5b, 0x7c,
0x76, 0x66, 0x22, 0xa6, 0x6d, 0xe9, 0x2b, 0xe9,
0x96, 0x46, 0x1d, 0x5e, 0x4d, 0xc8, 0x78, 0xef,
0x9b, 0xca, 0x03, 0x05, 0x21, 0xe8, 0x35, 0x1e,
0x4b, 0xae, 0xd2, 0xfd, 0x04, 0xf9, 0x46, 0x73,
0x68, 0xc4, 0xad, 0x6a, 0xc1, 0x86, 0xd0, 0x82,
0x45, 0xb2, 0x63, 0xa2, 0x66, 0x6d, 0x1f, 0x6c,
0x54, 0x20, 0xf1, 0x59, 0x9d, 0xfd, 0x9f, 0x43,
0x89, 0x21, 0xc2, 0xf5, 0xa4, 0x63, 0x93, 0x8c,
Kaukonen,Thayer Page [9]
Internet Draft ARCFOUR Algorithm July, 1999
0xe0, 0x98, 0x22, 0x65, 0xee, 0xf7, 0x01, 0x79,
0xbc, 0x55, 0x3f, 0x33, 0x9e, 0xb1, 0xa4, 0xc1,
0xaf, 0x5f, 0x6a, 0x54, 0x7f
Kaukonen,Thayer Page [10]
Internet Draft ARCFOUR Algorithm July, 1999
B. Sample Code
/* This code illustrates a sample implementation
* of the Arcfour algorithm
* Copyright (c) April 29, 1997 Kalle Kaukonen.
* All Rights Reserved.
*
* Redistribution and use in source and binary forms, with or
* without modification, are permitted provided that this copyright
* notice and disclaimer are retained.
*
* THIS SOFTWARE IS PROVIDED BY KALLE KAUKONEN AND CONTRIBUTORS ``AS
* IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL KALLE
* KAUKONEN OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
typedef struct
{
unsigned int x;
unsigned int y;
unsigned char state[256];
} ArcfourContext;
void arcfour_init(ArcfourContext *ctx, const unsigned char *key,
unsigned int key_len);
unsigned int arcfour_byte(ArcfourContext *ctx);
void arcfour_encrypt(ArcfourContext *ctx, unsigned char *dest,
const unsigned char *src, unsigned int len);
int main(int argc, char **argv)
{
unsigned char dest[500];
unsigned char mykey[] = {0x29, 0x04, 0x19, 0x72, 0xfb, 0x42,
0xba, 0x5f, 0xc7, 0x12, 0x77, 0x12,
0xf1, 0x38, 0x29, 0xc9};
unsigned char src[] = "Know thyself";
ArcfourContext mycontext;
/* Initialize the algoritm */
arcfour_init(&mycontext, mykey, 16);
/* Encrypt 13 bytes of the src string */
Kaukonen,Thayer Page [11]
Internet Draft ARCFOUR Algorithm July, 1999
arcfour_encrypt(&mycontext, dest, src, 13);
/* Now "dest" contains the encrypted string. Do whatever
you please with it... */
return 0;
}
void arcfour_init(ArcfourContext *ctx, const unsigned char *key,
unsigned int key_len)
{
unsigned int t, u;
unsigned int keyindex;
unsigned int stateindex;
unsigned char *state;
unsigned int counter;
state = ctx->state;
ctx->x = 0;
ctx->y = 0;
for (counter = 0; counter < 256; counter++)
state[counter] = counter;
keyindex = 0;
stateindex = 0;
for (counter = 0; counter < 256; counter++)
{
t = state[counter];
stateindex = (stateindex + key[keyindex] + t) & 0xff;
u = state[stateindex];
state[stateindex] = t;
state[counter] = u;
if (++keyindex >= key_len)
keyindex = 0;
}
}
unsigned int arcfour_byte(ArcfourContext *ctx)
{
unsigned int x;
unsigned int y;
unsigned int sx, sy;
unsigned char *state;
state = ctx->state;
x = (ctx->x + 1) & 0xff;
sx = state[x];
y = (sx + ctx->y) & 0xff;
sy = state[y];
ctx->x = x;
ctx->y = y;
state[y] = sx;
state[x] = sy;
Kaukonen,Thayer Page [12]
Internet Draft ARCFOUR Algorithm July, 1999
return state[(sx + sy) & 0xff];
}
void arcfour_encrypt(ArcfourContext *ctx, unsigned char *dest,
const unsigned char *src, unsigned int len)
{
unsigned int i;
for (i = 0; i < len; i++)
dest[i] = src[i] ^ arcfour_byte(ctx);
}
Kaukonen,Thayer Page [13]
Internet Draft ARCFOUR Algorithm July, 1999
C. Copyright Statement
Copyright (C) The Internet Society 1999. All Rights Reserved.
This document and translations of it may be copied and furnished to
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or assist in its implementation may be prepared, copied, published and
distributed, in whole or in part, without restriction of any kind,
provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
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in the Internet Standards process shall be followed, or as required to
translate it into languages other than English.
The limited permissions granted above are perpetual and will not be
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document and the information contained herein is provided on an "AS
IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK
FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT
LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL
NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY
OR FITNESS FOR A PARTICULAR PURPOSE.
This draft expires 9 December 1999.
Kaukonen,Thayer Page [14]