Cryptography Reference
In-Depth Information
Vigenere also introduced the concept of the one-time pad into cryptography.
The proliferation of computer communication in the 1960s brought with it an
increased demand to secure digital information. In addition, the involvement of the
private sector in providing digital security led to the work on symmetric ciphers by
Feistal at IBM that culminated in the most widely used encryption standard, known
as Data Encryption Standard (DES). In 1977, the National Institute of Standards and
Technology (NIST) adopted DES and published it as the Federal Information Processing
Standard 46 (FIPS PUB 46). Since then, many financial institutions accepted DES until
the emergence of the Advanced Encryption Standards (AES).
In 1976, Diffie and Hellman introduced a revolutionary concept in cryptography,
which led to the emergence of public key cryptography. In the next two sections of this
chapter, we review symmetric and asymmetric key cryptography.
4.1.1 Symmetric Key Cryptographic Systems
In symmetric key cryptography, the same key is used for encryption and decryption of
messages. Figure 4.1 depicts the symmetric key cryptography system.
In this example, the sender (Alice) uses a key (k) and encrypts the message (M) to
generate the cipher text (C). The cipher text is then sent over a public channel to the
receiver (Bob). The receiver (Bob) decrypts the cipher text (C) by using the same key
(k) and retrieves the message (M). However, this method has critical drawbacks, such as
the following:
Figure 4.1. Symmetric Key Cryptographic Model
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