cryptography

Cryptography

Cryptography refers to the encryption and decryption of communication between two entities or stored data. Encryption is a mathematical operation which converts the communication or data into unreadable forms, while decryption is the inverse operation of encryption.

There are many methods of encryption and decryption. Although these methods use different mathematical algorithms, one common ingredient is the existence of a "key." A key is a string of binary digits that controls the manner in which cryptography is performed. For non-recoverable encryption systems, decryption is impossible without knowledge of the key. For recoverable systems, decryption is possible without explicit knowledge of the key provided that key-recovery is performed.

Non-recoverable methods are in general more secure than recoverable methods. Examples of non-recoverable methods include:

Data Encryption Standard (DES)

DES is a standard method developed by the National Bureau of Standards to provide a standard method for protecting sensitive data. One single key is used to control the manner in which encryption is performed. Encryption is done in such a way that decryption is impossible without the key.

Pretty Good Privacy (PGP)

PGP is an implementation of the public-key cryptography system. In this system, a user is issued two keys: a public key P and a private key S. P and S are inverses of each other, i.e. S can decrypt a document that is encrypted by P. P and S together can be used to for encrypted communication or authentication of a document.

Kerberos

Kerberos is a software system for establishing a secure communication path over an otherwise insecure network. The data that are exchanged between network entities are encrypted using cryptography technologies such as DES. It is capable of user authentication and session encryption. Kerberos is often applied to telnet sessions.

References:

1) DES:

What is DES?

http://www.thenextwave.com/page19.html

DES: The Data Encryption Standard

http://www.cs.wm.edu/~hallyn/des/des.htm

2) PGP:

PGP and What It Does

http://www.arc.unm.edu/~drosoff/pgp/pgp.htm/

How to Get Better Policy on the Net?

http://www.cam.org/~githerr/privacy.htm

Internet Privacy Coalition