In order to provide varieties of security and efficiency levels, RC6 allows choices for the block size: 32 bits (for experimentation and evaluation purposes only), 64 bits (for use as a replacement for DES), and 128 bits (intended for AES). The number of rounds can range from 0 to 255, while the key sizes can range from 0 bits to 2040 bits in size.
RC6 is very similar to RC5 in structure and could be viewed as interweaving two parallel RC5 encryption processes. However, RC6 does use an extra multiplication operation not present in RC5 and the use of four b/4-bit working registers (see splitting of plaintext blocks in feistel cipher) instead of two b/2-bit registers as in RC5 (b is the block size). Integer multiplication is used to increase the diffusion achieved per round so that fewer rounds are needed and the speed of the cipher can be increased.<br>The reason for using four working registers instead of two is mainly for optimization on 32-bit CPUs. The default block size of RC5 was 64 bits, while the default block size of the AES is 128 bits. RC5 has only two working registers. It uses 32-bit operations when dealing with 64-bit blocks and 64-bit operations when dealing with 128-bit blocks, so four working registers are required to build the AES architecture using only 32-bit operations.
RC6 is a proprietary and patented algorithm (by RSA Security and ), and may require licensing and royalty payments for any products using the algorithm. It was designed by Ron Rivest, Matt Robshaw, Ray Sidney, and Yiqun Lisa Yin, and was also submitted to the NESSIE and CRYPTREC projects.
RC5
In cryptography, RC5 is a simple symmetric-key block cipher. Designed by Ronald Rivest in 1994, RC5 is a parameterized algorithm with a variable block size, a variable key size, and a variable number of rounds. ""RC"" stands for "Rivest Cipher", or alternatively, "Ron's Code".
In order to provide varieties of security and efficiency levels; RC5 has a variable block size (32, 64 or 128 bits), variable key size (0 to 2040 bits) and variable number of rounds (0 to 255). The original suggested choice of parameters were a block size of 64 bits, a 128-bit key and 12 rounds.
A key feature of RC5 is the use of data-dependent rotations; one of the goals of RC5 was to study and evaluate operations of block ciphers as a cryptographic primitive. RC5 also consists of a number of modular additions and eXclusive OR (Xor)s. The general structure of the algorithm is a Feistel-like network. The encryption and decryption routines can be specified in a few lines of code. The key schedule, however, is more complex, expanding the key using an essentially one-way function with the binary expansions of both e and the golden ratio as sources of "nothing up my sleeve numbers". The simplicity of the algorithm together with the novelty of the data-dependent rotations has made RC5 an attractive subject to study by cryptanalysts.
12-round RC5 (with 64-bit blocks) is susceptible to a differential attack using 2 chosen plaintexts. 18–20 rounds are suggested as sufficient protection.
RSA Security, which has a patent on the algorithm, offered a series of US$10,000 prizes for breaking ciphertexts encrypted with RC5, but these contests have been discontinued as of May 2007. A number of these challenge problems have been tackled using distributed computing, organised by Distributed.net. Distributed.net has brute-forced RC5 messages encrypted with 56- and 64-bit keys, and now is working on cracking a 72-bit key. At the current rate (as of November 12, 2008), it will take approximately 1,000 years to test every possible key to complete the project.
Altaic languages
Altaic is a disputed language family, but only a few linguists still believe that it existed. It supposedly had 66 languages that are now spoken by about 348 million people, mostly in and around Central Asia and northeast Asia.
According to the most well-known classification, Altaic has the Turkic languages, Mongolic, and the Tungusic languages. That is probably the meaning attributed to "Altaic" by most general linguists.
However, since the publication of Gustaf John Ramstedt's "Einführung" in 1952–1957, most Altaicists have included Korean in Altaic. Since the publication of Roy Andrew Miller's "Japanese and the Other Altaic Languages" in 1971, some also included Japanese (Nicholas Poppe) or Japonic, consisting of Japanese and Ryukyuan.
A few linguists (such as (Street 1962)) even count Ainu with the Altaic languages but as part of a node including Korean and Japanese, in contrast to a Turkic-Mongolic-Tungusic node, with Korean-Japanese-Ainu and Turkic-Mongolic-Tungusic, in turn, forming a higher-level node.
The core version of Altaic, consisting of Turkic, Mongolic, and Tungusic, is sometimes referred to as "Micro-Altaic," and the expanded version, including Korean and sometimes Japanese, is referred to as "Macro-Altaic," but even the core version is very controversial.
Mongolian language
The Mongolian language (, "Mongol kele", Cyrillic: Монгол хэл, "Mongol khel") is the best-known member of the Mongolic language family and the language of most of the residents of Mongolia, where it is officially written with the Cyrillic alphabet and of around three million Mongolian speakers in the "Inner Mongolia Autonomous Region" of China, where it is officially written with the traditional Mongolian script. It is also spoken in some areas in the Russian Far East and Kyrgyzstan. The majority of speakers in Mongolia speak the Khalkha (or "Halh") dialect, while those in China speak one of many Inner Mongolian dialects.
RC2
In cryptography, RC2 is a symmetric-key block cipher. Designed by Ronald Rivest in 1987. ""RC"" stands for "Rivest Cipher", or alternatively, "Ron's Code".
RC2 is a 64-bit block cipher with a variable key size and using 18 rounds.
Rounds are arranged as a source-heavy feistel network, with 16 rounds of one type called ""mixing rounds"" interleaved by two rounds of another type called ""mashing rounds"".
The 18 rounds are performed using the following interleaved sequence:
RC2 uses "key-expansion algorithm" by which an expanded key consisting of 64 (16-bit words) is produces depending in a complicated way on every bit of the supplied ""variable-length"" input key. A mixing round consists of four applications of the ""mix-up"" transformation, as shown in the diagram. A round is ""mashed"" by adding to it one of the 16-bit words of the expanded key (RFC 2268).
RC2 is susceptible to a related-key attack using 2 chosen-plaintext attacks (Kelsey "et al.", 1997).
The development of RC2 was sponsored by Lotus, who were seeking a custom cipher be exported as part of their Lotus Notes software, after evaluation by the NSA. The NSA suggested a couple of changes, which Ronald Rivest incorporated. After further negotiations, the cipher was approved for export in 1989.
Along with RC4, RC2 with a 40-bit key size was treated under US export regulations for cryptography. Now all 40-bit encryption algorithms are obsolete because they are dangerously susceptible to brute force attacks.
Initially, the details of the algorithm were kept secret — proprietary to RSA Security — but on 29 January 1996, source code for RC2 was anonymously posted to the Internet on the Usenet forum, sci.crypt. A similar post had occurred earlier with RC4. It is unclear whether the poster had access to the specifications or whether it had been reverse engineered.
1999 East Timorese crisis
The 1999 East Timorese crisis was a conflict. Militia who did not like the independence in East Timor started the conflict when they attacked civilians. These attacks led to more violence all over the country. Most of the violence occurred in the capital Dili.