Editing Red Pike (cipher)

{{Short description|Block cipher}}
'''Red Pike''' is a [[classified information|classified]] [[United Kingdom]] government encryption algorithm, proposed for use by the [[National Health Service]] by [[GCHQ]], but designed for a "broad range of applications in the [[Her Majesty's Government|British government]]" [http://www.cs.berkeley.edu/~daw/rja/GCHQ/25_2_97.htm] {{Webarchive|url=https://web.archive.org/web/20040423194646/http://www.cs.berkeley.edu/~daw/rja/GCHQ/25_2_97.htm |date=2004-04-23 }}. Little is publicly known about Red Pike, except that it is a [[block cipher]] with a 64-bit [[block size (cryptography)|block size]] and 64-bit [[key length]].  According to the academic study of the cipher cited below and quoted in a paper by [[Ross J. Anderson|Ross Anderson]] and [[Markus Kuhn (computer scientist)|Markus Kuhn]], it "uses the same basic operations as [[RC5 encryption algorithm|RC5]]" (add, XOR, and left shift) and "has no look-up tables, virtually no key schedule and requires only five lines of code"; "the influence of each key bit quickly cascades" and "each encryption involves of the order of 100 operations". 64 bits of key entropy are not considered secure anymore.

Red Pike is available to approved British government contractors in software form, for use in confidential (not secret) government communication systems. GCHQ also designed the [[Rambutan (cryptography)|Rambutan]] cryptosystem for the same segment.

Given that Red Pike is a British encryption algorithm, its name likely refers to a particular [[Red Pike (Buttermere)|fell in the western English Lake District]].

==Supposed source code==
In February 2014, the supposed source code for Red Pike was posted as follows to the [[Cypherpunk]] mailing list.
<ref>[http://permalink.gmane.org/gmane.comp.security.cypherpunks/3680 "Red Pike cipher"], Red Pike cipher, Cypherpunk mailing list, Gmane</ref>
<syntaxhighlight lang="c">
 /* Red Pike cipher source code */
 
 #include <stdint.h>
 
 typedef uint32_t word;
 
 #define CONST 0x9E3779B9
 #define ROUNDS 16
 
 #define ROTL(X, R) (((X) << ((R) & 31)) | ((X) >> (32 - ((R) & 31))))
 #define ROTR(X, R) (((X) >> ((R) & 31)) | ((X) << (32 - ((R) & 31))))
 
 void encrypt(word * x, const word * k)
 {
   unsigned int i;
   word rk0 = k[0];
   word rk1 = k[1];
 
   for (i = 0; i < ROUNDS; i++)
   {
     rk0 += CONST;
     rk1 -= CONST;
 
     x[0] ^= rk0;
     x[0] += x[1];
     x[0] = ROTL(x[0], x[1]);
 
     x[1] = ROTR(x[1], x[0]);
     x[1] -= x[0];
     x[1] ^= rk1;
   }
 
   rk0 = x[0]; x[0] = x[1]; x[1] = rk0;
 }
 
 void decrypt(word * x, const word * k)
 {
   word dk[2] =
   {
     k[1] - CONST * (ROUNDS + 1),
     k[0] + CONST * (ROUNDS + 1)
   };
 
   encrypt(x, dk);
 }
</syntaxhighlight>
==See also==
* [[Type 1 product]]

==References==
{{Reflist}}
* C Mitchell, S Murphy, F Piper, P Wild. (1996). Red Pike &mdash; an assessment. Codes and Ciphers Ltd 2/10/96.
* [http://cryptome.org/jya/akdfa.txt Paper by Anderson and Kuhn which includes excerpts from (Mitchell et al., 1996)].  Another version is {{cite conference|last1=Anderson|first1=Ross|last2=Kuhn|first2=Markus|year=1997|title=Low Cost Attacks on Tamper Resistant Devices|book-title=Security Protocols, 5th International Workshop|pages=125&ndash;136|url=http://www.cl.cam.ac.uk/~rja14/Papers/tamper2.pdf}}
* [http://www.cypherspace.org/adam/ukexport/zergo.html "The use of encryption and related services with the NHSnet"]

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[[Category:Block ciphers]]
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