Also found in: Acronyms, Wikipedia.


A cipher designed by RSA Data Security, Inc. which can accept keys of arbitrary length, and is essentially a pseudo random number generator with the output of the generator being XORed with the data stream to produce the encrypted data. For this reason, it is very important that the same RC4 key never be used to encrypt two different data streams. The encryption mechanism used to be a trade secret, until someone posted source code for an algorithm onto Usenet News, claiming it to be equivalent to RC4. The algorithm is very fast, its security is unknown, but breaking it does not seem trivial either. There is very strong evidence that the posted algorithm is indeed equivalent to RC4.

The United States government routinely approves RC4 with 40-bit keys for export. Keys this small can be easily broken by governments, criminals, and amateurs. The exportable version of Netscape's Secure Socket Layer, which uses RC4-40, was broken by at least two independent groups. Breaking it took about eight days; in many universities or companies the same computing power is available to any computer science student.

See also Damien Doligez's SSL cracking page, RC4 Source and Information, SSLeay, Crypto++, Ssh, A collection of articles.
This article is provided by FOLDOC - Free Online Dictionary of Computing (foldoc.org)

RC algorithms

(Ron's Code or Rivest's Cipher algorithms) A family of secret-key cryptographic algorithms from RSA Security, Inc., Bedford, MA (www.rsa.com). Although RSA (formerly RSA Data Security and acquired by EMC in 2006) is widely known for its public key methods, its secret key algorithms are also widely used. Ronald Rivest is the "R" in RSA.

Designed as a replacement for DES, RC2 uses a variable key and the block cipher method. RC4 uses a variable key and stream cipher method. Both RC5 and RC6 are block ciphers with variable keys up to 2,040 bits. RC6, designed by Rivest and others, uses integer multiplication for improved performance. RC6 was created to conform to the AES standard and was a finalist in the competition for the AES algorithm. See RSA, EMC, AES and DES.
Copyright © 1981-2019 by The Computer Language Company Inc. All Rights reserved. THIS DEFINITION IS FOR PERSONAL USE ONLY. All other reproduction is strictly prohibited without permission from the publisher.
References in periodicals archive ?
The algorithm used to encrypt and decrypt XML structures is the RC4 algorithm.
The RC4 algorithm was proposed by Ron Rivest in 1987 and kept secret as a trade until it was leaked in 1994 [10].
In the case of future situation (Table 7), the future rule curves (RC4 and RC5) showed the best performance, as indicated by the frequency of the water shortage and the average and the maximum magnitudes of the water shortages.
OSCO HTPC Server AES-256 32.05 18.66 112.46 AES-192 35.7 22.11 129.48 AES-128 41.53 25.59 152.48 3DES 7.71 11.98 32.66 DES 19.85 33.54 84.8 IDEA 25.16 25.05 105.71 Blowfish 32.6 62.4 143.36 RC4 77.05 123.15 713.01 Note: Table made from bar graph.
In PC, the stalk : trash ratio was 0.81, decreasing to 0.77 and 0.69 in RC1 and RC4 respectively (Table 1).
Stream cipher examples are: RC4, one-time pad or Vernam cipher, and so forth.
The subfractions RC4 (diethyl ether), RC5 (ethyl acetate), and RC6 (n-butanol) contained a wide variety of phenolic acids [2, 5, 9, 11, 12, 16, 22, 31 and 32], flavonoids, mainly, quercetin [18, 19, 26 and 34], and kaempferol [25, 27, 30, 33 and 35] derivatives, as well as ellagitannins and related compounds [4, 6-8, 14 and 29].
Algorithm 1 N = 20000; K = randi([0 2541, 1, 255); S = [0: 255-1]; j = 0; for i = 1: 255 j = mod(j + S(i) + K(i), 255); Sk = S(j + 1); S(j + 1) = S(i); S(i) = Sk; end C = zeros(1, N); j = 0; i = 0; k = 1; for l = 1:N/8 i = mod(I + 1, 255); j = mod(j + S(i + 1), 255); Sk = S(j + 1); S(j + 1) = S(i + 1); S(i + 1) = Sk; C(l) = S(mod(S(j + 1) + S(i + 1), 255) + 1); end C = (dec2bin(C))'; C = C(:); C = bin2dec(C); Consequently, the RC4 algorithm PRNG is designed.
M-FAST Turkish Form internal reliability analysis and Cronbach alpha coefficients Number of Items Cronbach's Alpha 25 .93 M-FAST items Cronbach's Alpha value (when every item is excluded) RO1 .92 ES1 .92 RC1 .92 UH1 .92 ES2 .93 UH2 .92 RO2 .92 ES3 .92 UH3 .92 ES4 .92 RO3 .92 RC2 .92 ES5 .93 USC1 .92 ES6 .92 RC3 .92 RC4 .92 RC5 .92 ES7 .92 UH4 .92 UH5 .92 RC6 .92 N11 .93 RC7 .92 S1 .92 RO: Reported or Observed, ES: Extreme Symptomatology, RC: Rare Combinations, UH: Unusual Hallucinations, USC: Unusual Symptom Course, NA: Negative Image, S: Suggestibility.
This new version expands these document filters to directly support a broader range of encrypted PDFs, covering PDF files encrypted with an owner password up to 128-bit RC4 and 128-bit and 256-bit AES.