The term "cipher" (sometimes "cypher") is often used to refer to a pair of (encryption/decryption) algorithms. Therefore, the term "cryptosystem" is most often used when the key generation algorithm is important. For this reason, the term "cryptosystem" is commonly used to refer to public key techniques; however both "cipher" and "cryptosystem" are used for symmetric key techniques.
The "Internet Security Glossary" RFC 2828 advises against using the term "cryptosystem", giving the following definitions.
Serpent (cipher)
Serpent is a symmetric key block cipher which was the second finalist in the Advanced Encryption Standard (AES) contest after Rijndael. Serpent was designed by Ross Anderson, Eli Biham, and Lars Knudsen.
Serpent has a block size of 128 bits and supports a key size of 128, 192 or 256 bits. The cipher is a 32-round substitution-permutation network operating on a block of four 32-bit words. Each round applies one of eight 4-bit by 4-bit S-boxes 32 times in parallel. Serpent was designed so that all operations can be executed in parallel, using 32 1-bit slices. This maximizes parallelism, but also allows use of the extensive cryptanalysis work performed on DES.
Serpent was widely viewed as a more traditional approach to security than the other AES finalists choosing a larger security margin: the designers estimated 16 rounds to be sufficient against known types of attack, but specified 32 rounds as insurance against future progress in cryptanalysis.
The Serpent cipher has not been patented. It is completely placed in the public domain and can be freely used by anyone.
The 32 rounds make Serpent more secure than Rijndael; however, Rijndael with 10 rounds is faster and easier to implement for small Block ciphers and on embedded system. For that reason, Rijndael was selected as the winner in the AES competition.
The XSL attack, if effective and would weaken Serpent (though not as much as it would weaken Rijndael, which became AES). However, many cryptanalysts believe that if implementations considered to overcome the XSL attack, the XSL attack would be more difficult than a brute force attack.
Pretty Good Privacy
Pretty Good Privacy (PGP) is a computer program that provides cryptographic and authentication. PGP is often used for signing, encrypting and decrypting electronic mails (e-mails) to increase the security of e-mail communications. It was originally created by Phil Zimmermann in 1991.
PGP and other similar products follow the OpenPGP standard (RFC 4880) for encrypting and decrypting data.
OpenPGP is on the Internet Standards Track; the current specification is RFC 4880 (November 2007). OpenPGP is still under development and the successor to RFC 2440, which is RFC 4880, has been made a proposed standard. Many e-mail clients provide "OpenPGP-compliant" email security as described in RFC 3156.
The Free Software Foundation has developed its own "OpenPGP-compliant" program called GNU Privacy Guard (abbreviated GnuPG or GPG). GnuPG is freely available together with all source code under the GNU General Public License (GPL) and is maintained separately faraway from several Graphical User Interfaces (GUIs) that interact with the GnuPG library for encryption, decryption and signing functions (see KGPG, Seahorse, MacGPG). Several other vendors have also developed "OpenPGP-compliant" software.
Weak key
In cryptography, a weak key is a key which when used with a specific cipher, makes the cipher behave in some undesirable way, and simplifies breaking (cracking) the ciphertext.
Weak keys usually represent a very small fraction of the overall key space, which means that if someone generates a random key to encrypt a message, it is a rare condition that weak keys will cause a security problem. However, it is considered a good design for a cipher to have no weak keys ("quality chiper"). A cipher with no weak keys is said to have a "flat", or "linear", key space.
XSL attack
In cryptography, the XSL attack is a method of cryptanalysis for block ciphers. The attack was first published in 2002 by researchers Nicolas Courtois and Josef Pieprzyk. It was claimed that it may break the Advanced Encryption Standard (AES) cipher faster than a brute force attack.
AES is already widely used in commerce and government for the transmission of secret and classified information. Finding a technique that can decrease the amount of time it takes to break the secret message without having the key could cause wide damage.
In 2004 it was shown by one of the cryptanalysts, that the algorithm does not perform as described in its published paper. In addition, the method requires long effort. Unless shortened, the technique does not reduce the effort to break AES in comparison to a brute force attack. Therefore, it does not affect the real-world security of block ciphers in the near future. However, the attack has caused some experts to insert complexities in the algebraic simplicity of the current AES.
The XSL attack relies on first analyzing the "internal design" of a cipher then deriving a system of quadratic simultaneous equations. These systems of equations are typically very large, for example 8000 equations with 1600 variables for the 128-bit AES. Several methods for solving such systems are known. In the XSL attack, a specialized algorithm, termed XSL (eXtended Sparse Linearization), is then applied to solve these equations and compute the key.
The attack is well-known and famous for requiring only a handful of known plaintexts to perform. Previous methods of cryptanalysis, such as linear and differential cryptanalysis, often require unrealistically large numbers of known or chosen plaintexts, which make them impossible to realize.
Sound the Alarm
Sound the Alarm is the fifth studio album by the emo band Saves the Day. It was released by Vagrant Records on April 11, 2006. It was produced by Steve Evetts who also produced Saves the Day's first two albums, "Can't Slow Down" and "Through Being Cool". All of the album's lyrics were written by Chris Conley. It is their darkest album, and Chris wrote it about the black clouds in his life, and things that were eating him alive. This album was welcomed by many as something of a return to the band's classic sound, after the sonic departure of "In Reverie" in 2003.
"Sound the Alarm" reached number 67 on the Billboard 200 Album Chart.
"Sound the Alarm" is part one of a three part concept that Conley described in an interview with Punknews.org. It is their trilogy about self discovery.
The "Head for the Hills" track is used on the soundtrack of the football video game "Madden NFL 07".
Ennis
Ennis is a town in the Republic of Ireland. It has about 25,000 people living in it. There are people from eastern Europe, Africa and the United Kingdom living in Ennis.
Ennis has a bus and railway station.
The town was once small but has grown much because of an economic boom, which has now ended.
Trey Parker
Randolph Severn "Trey" Parker III (born October 19 1969) is an American animator, screenwriter, film director, voice actor, actor, musician and Academy Award nominated lyricist. He and Matt Stone worked on the animated series "South Park".
Matt Stone
Matthew Richard "Matt" Stone (born May 26, 1971) is an Academy Award- nominated Emmy Award- winning American animator, screenwriter, director, producer, voice actor, musician and actor. He and Trey Parker created the animated television series, "South Park".
Treaty of friendship and alliance between the Government of Mongolia and Tibet
Tibet and Mongolia signed a treaty called the Treaty of friendship and alliance between the Government of Mongolia and Tibet on February 2, 1913, at Urga (now Ulaanbaatar). Today, we are not sure if the treaty can be used or not.