Tool to code / decode RC4 messages. Rivest Cipher 4 is a fast symmetric encryption algorithm created by Ronald Rivest used in some protocols like TLS or WEP.

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.

Tool to code / decode RC4 messages. Rivest Cipher 4 is a fast symmetric encryption algorithm created by Ronald Rivest 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, ARC4, Alleged **RC4** or Ron's Code 4.

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

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

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