Tool for encoding / decoding with the RC4 (Rivest Cipher 4) algorithm used in particular in the TLS (Transport Layer Security) protocol.

RC4 Cipher - dCode

Tag(s) : Modern Cryptography

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The RC4 was created to be symmetric, the encryption phase is identical to decryption, use the form above.

RC4 for Rivest Cipher 4 is a symmetric and fast cipher algorithm, well suited to binary data, created by Ronald Rivest and used in some protocols like TLS or WEP.

The RC4 digit uses a key that can initialize an array of 256 boxes.

The algorithm that allows to initialize the array with the key `key` is:

`// Pseudocode`

for i = 0 -> 255 {

t[i] = i

}

j = 0

k = length(cle)

for i = 0 -> 255 {

j = (j + t[i] + key[i % k]) % 256

swap t[i] <-> t[j]

}

The array `t` can then be used to generate a stream by moving values and XOR operation.

The RC4 algorithm is then:` // Pseudocode`

a = b = 0

j = length(string)

codes = []

for i = 0 -> j {

a = (a + 1) % 256

b = (b + t[a]) % 256

swap t[a] <-> t[b]

codes []= ( t[ (t[a] + t[b]) % 256] ) XOR string[i]

}

print codes

The codes are values between 0 and 255.

__Example:__ `dCode` (`64,43,6F,64,65` in hexadecimal) encrypted with the key `RC4` (`52,43,34` in hexadecimal) is coded `2B,7F,DA,B6,1D` (hexadecimal)

Identically `2B,7F,DA,B6,1D` (in hexadecimal) decrypted with the same key `RC4` (`52,43,34` in hex) becomes `64,43,6F,64,65` (`dCode` in ASCII)

Decryption is exactly the same as encryption.

The codes generated by RC4 are between 0 and 255, usually represented in hexadecimal.

RC4 is pseudo-random, there is no easily detectable bias.

The code is also called RCfour, ARCFour, ARC4, Alleged RC4 or Ron's Code 4.

Any reference to WEP or TLS protocols is a clue.

RC4 was invented by Ronald Rivest (one of the inventors of RSA encryption) in 1987.

dCode retains ownership of the "RC4 Cipher" source code. Except explicit open source licence (indicated Creative Commons / free), the "RC4 Cipher" algorithm, the applet or snippet (converter, solver, encryption / decryption, encoding / decoding, ciphering / deciphering, breaker, translator), or the "RC4 Cipher" functions (calculate, convert, solve, decrypt / encrypt, decipher / cipher, decode / encode, translate) written in any informatic language (Python, Java, PHP, C#, Javascript, Matlab, etc.) and all data download, script, or API access for "RC4 Cipher" are not public, same for offline use on PC, mobile, tablet, iPhone or Android app!

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Cite as source (bibliography):

*RC4 Cipher* on dCode.fr [online website], retrieved on 2024-09-10,

rc4,arcfour,arc4,rivest,tls,wep

https://www.dcode.fr/rc4-cipher

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