DES and 3DES

Data Encryption Standard (DES), encryption of data over the blocks with a 64-bit 56-bit key. The DES algorithm takes the input of a series of transformations: the exchange, a complex function, both permutation and substitution and depends on a key input, a simple permutation function that switches the two halves of the data, the function is applied again, and a permutation function, which is the reverse of the first permutation. There are five"Modes" that were defined in terms of, DES, a variety of applications. Six Electronic Codebook, Cipher Block Chaining, Cipher Feedback, comments and counter output (the concept of encryption, 2005).

Triple-DES or 3DES includes repetition of the DES algorithm three times in the plains, with two or three different keys to produce the ciphertext. As mentioned in this article of the dead. Long live ... Well, uh, that, "the first encrypted and then decryptedFinally, it is encrypted again "(Moskowitz, 1999). Three DES is used because it is very resistant to cryptanalysis, serves as an alternative to protect against the potential vulnerability of DES to add to brute force attack. Triple-DES has been adopted for the use of key management standard ANSI X 9.17 and ISO 8732, along with a series of Internet-based applications such as PGP and S / MIME (AES, encryption and confidentiality, 2005). The figure below shows the triple encryption andthe central part of the exhibition on how to 3DES decryption instead of encryption makes it more secure.

Nonce and a Key Distribution Center (KDC) shares a secret key or master key between the parties over a network. The KDC is responsible for the nonce and key generation for a short time on a connection between two parties, are used as session keys known, and for the distribution of key the master key to protect the distribution. The following steps take place:

1. A request for applicationsthe KDC for a session key with B. The message contains the identity of A and B, as well as a unique identifier for the operation, a nonce, which may include a random number or a counter.

2. The KDC responds with a message encrypted by Ka So, only one can read the message and know that the message originated from the KDC. The message contains:

• The one-time session key, KS, to be used for the session.
• The original message request, including the nonce, so that AMatch this response with a request.

In addition, the message contains two terms for the states B:

• The one-time session key, KS.
• An identifier of A, IDA.

These are encrypted with the master key that the KDC shares with B. sent to B, to make connections and to prove their identity.

3. One stores the session key for use in the upcoming session and forwards to B the information that emerged from the KDC to B. This information is protectedagainst eavesdropping, since it is encrypted with the master key, Kb B knows the session key, identity, and that information from the KDC.

4. B sends a nonce, N2, A, with a freshly baked session key for encryption.

5. With the session key, A responds with f (N2), where f is a function that performs a transformation of N2 (ie, add one) (Stallings, 2003 PGS 214-15) is.

As a result of the above mentioned, such as DES, operates, uses 3DES is why now, because the3DES is a central part of the encryption and decryption rather than explain, a nonce and a key distribution center.

Works Cited

Moskowitz, Robert. (1999). DES is dead. Long Live ... well, uh, what? Network Computing, vol. 10 Issue 6 Retrieved 22nd October 2005, from, EBSCO Host Research Database on [http://web10.epnet.com]

Stallings, William. (2003). Cryptography and Network Security: Principles and Practice. New Jersey: Pearson Education, Inc.

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