Portable or "traveller mode" means the encryption software can be run without installation to the system hard drive. In this mode, the software typically installs a temporary driver from the portable media. Since it is installing a driver (albeit temporarily), administrative privileges are still required.

more...

Full disk encryption (or whole disk encryption) is a kind of disk encryption software or hardware which encrypts every bit of data that goes on a disk or disk volume. The term "full disk encryption" is often used to signify that everything on a disk is encrypted, including the programs that can encrypt bootable operating system partitions.

more...

With full disk encryption, the decision of which individual files to encrypt is not left up to users' discretion. This is important for situations in which users might not want or might forget to encrypt sensitive files.

more...

Immediate data destruction, as simply destroying the cryptography keys renders the contained data useless. However, if security towards future attacks is a concern, purging or physical destruction is advised.

more...

The cost of computing a hash function must be small enough to make a hashing-based solution more advantageous over other approaches. For instance, binary search can locate an item in a sorted table of n items with log2 n key comparisons. Therefore, a hash-table solution will be more efficient than binary search only if computing the hash function for one key costs less than performing log2 n key comparisons. Most cryptographic hash functions are too slow by this criterion.

more...

The same technique can be used to map two-letter country codes like 'us' or 'za' to country names (26²=676 table entries), 5-digit zip codes like 13083 to city names (100000 entries), etc. Invalid data values (such as the country code 'xx' or the zip code 00000) may be left undefined in the table, or mapped to some appropriate 'null' value.

more...

A hash function that is injective — that is, maps each valid input to a different hash values — is said to be perfect. With such a function one can directly locate the desired entry in a hash table, without any additional searching.

more...

One can adapt certain checksum or fingerprinting algorithms for use as hash functions. Some of those algorithms will map arbitrary long string data z, with any typical real-world distribution — no matter how non-uniform and dependent — to a 32-bit or 64-bit string, from which one can extract a hash value in 0 through n-1.

more...

Although several of the forms of EKE in this paper were later found to be flawed, the surviving, refined, and enhanced forms of EKE effectively make this the first method to amplify a shared password into a shared key, where the shared key may subsequently be used to provide a zero-knowledge password proof or other functions.

more...

Password-authenticated key retrieval is a process in which a client obtains a static key in a password-based negotiation with a server that knows data associated with the password, such as the Ford and Kaliski methods. In the most stringent setting, one party uses only a password in conjunction with two or more (N) servers to retrieve a static key, in a way that protects the password (and key) even if any N-1 of the servers are completely compromised.

more...

Essentially all ciphers remained vulnerable to cryptanalysis using this technique until the development of the polyalphabetic cipher, most clearly by Leon Battista Alberti around the year 1467, though there is some indication that it was known to earlier Arab mathematicians such as Al-Kindi.[6] Alberti's innovation was to use different ciphers (i.e., substitution alphabets) for various parts of a message (perhaps for each successive plaintext letter in the limit).

more...

He also invented what was probably the first automatic cipher device, a wheel which implemented a partial realization of his invention. In the polyalphabetic Vigenère cipher, encryption uses a key word, which controls letter substitution depending on which letter of the key word is used. In the mid 1800s Babbage showed that polyalphabetic ciphers of this type remained partially vulnerable to extended frequency analysis techniques

more...

Nonetheless, good modern ciphers have stayed ahead of cryptanalysis; it is typically the case that use of a quality cipher is very efficient (i.e., fast and requiring few resources), while breaking it requires an effort many orders of magnitude larger than before, making cryptanalysis so inefficient and impractical as to be effectively impossible.

more...

In recent times, IBM personnel designed the algorithm that became the Federal (ie, US) Data Encryption Standard; Whitfield Diffie and Martin Hellman published their key agreement algorithm,[9]; and the RSA algorithm was published in Martin Gardner's Scientific American column.

more...

Cryptography is, also, a branch of engineering, but an unusual one as it deals with active, intelligent, and malevolent opposition (see cryptographic engineering and security engineering); most other kinds of engineering need deal only with neutral natural forces. There is also active research examining the relationship between cryptographic problems and quantum physics (see quantum cryptography and quantum computing).

more...

That internal state is initially set up using the secret key material. RC4 is a widely used stream cipher; see Category:Stream ciphers.[10] Block ciphers can be used as stream ciphers; see Block cipher modes of operation. Cryptographic hash functions are a third type of cryptographic algorithm. They take a message of any length as input, and output a short, fixed length hash which can be used in (for example) a digital signature.

more...

It was named after Julius Caesar who is reported to have used it, with a shift of 3, to communicate with his generals during his military campaigns, just like EXCESS-3 code in boolean algebra. Some of the existing work-around designs work, more or less, but are not fully satisfactory.

more...

Bob verifies that R can be encrypted with the bank's public key by computing R' = Re(mod n), which means that Alice has deposited $100 into the bank. Bob then sends this value to the bank and the bank checks its records to be sure that R has not been already used. If it has not, it deposits $100 into his account and updates its database that the unique value R has been redeemed.

more...

There are several strategies which contribute to making the e-mail so handled (more, or less) anonymous. In general, different classes of anonymous remailers differ with regard to the choices their designers/operators have made. These choices can be influenced by the legal ramifications of operating specific types of remailers

more...

Serpent is a symmetric key block cipher which was a finalist in the Advanced Encryption Standard (AES) contest, where it came second to Rijndael. Serpent was designed by Ross Anderson, Eli Biham, and Lars Knudsen.

more...