The study authors were able to demonstrate a cold boot attack to recover cryptographic keys for several popular disk encryption systems despite some memory degradation, by taking advantage of redundancy in the way keys are stored after they have been expanded for efficient use.

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This fundamental principle was first explicitly stated in 1883 by Auguste Kerckhoffs and is generally called Kerckhoffs' principle; alternatively and more bluntly, it was restated by Claude Shannon, the inventor of information theory and the fundamentals of theoretical cryptography, as Shannon's Maxim — 'the enemy knows the system'.

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The term cypherpunk, derived from cipher and punk, was coined by Jude Milhon as a pun to describe cyberpunks who used cryptography. [1] In November 2006, the word was proposed for inclusion in the Oxford English Dictionary[2]. The Cypherpunks included several notable computer industry figures

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Blowfish's key schedule starts by initializing the P-array and S-boxes with values derived from the hexadecimal digits of pi, which contain no obvious pattern (see nothing up my sleeve number). The secret key is then XORed with the P-entries in order (cycling the key if necessary). A 64-bit all-zero block is then encrypted with the algorithm as it stands.

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Many encryption algorithms exist. The more popular options were submitted to the National Institute of Standards and Technology or NIST for the Advanced Encryption Standard (AES) competition. The winner, Rijndael, got 86 votes while Serpent got 59 votes, Twofish 31 votes, RC6 23 votes and MARS 13 votes. NIST chose Rijndael as its standard. Serpent and Rijndael are in fact somewhat similar; the main difference is that Rijndael is faster (having fewer rounds) but Serpent is more secure.

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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 to 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.

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Symmetric-key algorithms are generally much less computationally intensive than asymmetric key algorithms. In practice, asymmetric key algorithms are typically hundreds to thousands times slower than symmetric key algorithms.

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However, some checksums fare poorly in the avalanche test, which may be a concern in some applications. In particular, the popular CRC32 checksum provides only 16 bits (the higher half of the result) that are usable for hashing. Moreover, each bit of the input influences only one bit of the CRC32; so care must be taken to use all 32 bits when computing the hash from the checksum.

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In these applications, the set of all inputs is some sort of metric space, and the hashing function can be interpreted as a partition of that space into a grid of cells. The table is often an array with two or more indices (called a grid file, grid index, bucket grid, and similar names), and the hash function returns an index tuple. This special case of hashing is known as geometric hashing or the grid method.

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There are several factors that affect the choice of an encryption algorithm including speed and security. The purpose of disseminating an encryption method is to allow the community to evaluate it. If it is indeed secure, then its power lies in the fact that its method has been subjected to scrutiny and found to be sound, not that it is secret.

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The Hardware-based Full Disk Encryption solutions are considerably faster than the software-based solutions, and usually produce no overhead for the CPU or the hard disk drive. Hardware-based Full Disk Encryption, without some form of user authentication, provides absolutely no protection of data. Currently, there are two solutions providing Pre-Boot Authentication for Hardware-based Full Disk Encryption and a BIOS or ATA password can provide basic access control.

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The encryption key is trivially related to the decryption key, in that they may be identical or there is a simple transform to go between the two keys. The keys, in practice, represent a shared secret between two or more parties that can be used to maintain a private information link.

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In the most stringent password-only security models, there is no requirement for the user of the method to remember any secret or public data other than the password. Augmented PAKE is a variation applicable to client/server scenarios, in which an attacker must perform a successful brute-force attack in order to masquerade as the client using stolen server data.

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One rare success has been Hong Kong's Octopus card system, which started as a transit payment system and has grown into a widely used electronic cash system. Singapore also has an electronic money implementation for its public transportation system (commuter trains, bus, etc), which is very similar to Hong Kong's Octopus card and based on the same type of card (FeliCa). There is also one implementation in the Netherlands, known as Chipknip.

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However, lack of randomness in those generators or in their initialization vectors is disastrous and has led to cryptanalytic breaks in the past. Therefore, it is essential that an implementation uses a source of high entropy for its initialization.

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Hardware solutions have also been criticised for being poorly documented. Many aspects of how the encryption is done are not published by the vendor. This leaves the user with little possibility to judge the security of the product. It also increases the risk of a vendor lock-in.

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Technically electronic or digital money is a representation, or a system of debits and credits, used to exchange value, within another system, or itself as a stand alone system, online or offline. Also sometimes the term electronic money is used to refer to the provider itself. A private currency may use gold to provide extra security, such as digital gold currency.

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There are multiple tools available in the market that allow for full disk encryption. However, they vary greatly in features and security. They are divided into two main categories: hardware-based and software-based. Comparison of disk encryption software.

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The Data Encryption Standard (DES) is a block cipher (a form of shared secret encryption) that was selected by the National Bureau of Standards as an official Federal Information Processing Standard (FIPS) for the United States in 1976 and which has subsequently enjoyed widespread use internationally.

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This class includes the so-called acoustic fingerprint algorithms, that are used to locate similar-sounding entries in large collection of audio files (as in the MusicBrainz song labeling service). For this application, the hash function must be as insensitive as possible to data capture or transmission errors, and to "trivial" changes such as timing and volume changes, compression, etc.

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