Cryptology  (from the Greek krypts, "hidden," and lgos, "word") is the science of secure (generally secret)  communications?
Cryptography (from the Greek krypts and grphein, "to write") is the study of the principles and techniques by which information can be concealed in ciphers and later revealed by legitimate users employing the secret key?
Cryptanalysis (from the Greek krypts and analein, "to loosen" or "to untie") is the science (and art) of recovering information from ciphers without knowledge of the key?
Cryptography was concerned initially with providing secrecy for written messages?
There are two basic kinds of mathematical operations used in cipher systems: transpositions and substitutions?
Transpositions rearrange the symbols in the plaintext without changing the symbols themselves?
Substitutions replace plaintext elements (symbols, pairs of symbols, etc.) with other symbols or groups of symbols without changing the sequence in which they occur.?
The purpose of encryption is to render a document unreadable by all except those authorized to read it?
The content of the original document, referred to by cryptographers as "plaintext," is scrambled using an algorithm and a variable, or key?
The key is a randomly selected string of numbers; generally speaking, the longer the string, the stronger the security?
Vernam's one-time pad is an example of symmetric encryption, in which the same key is used to both encode and decode a message?
For some encryption algorithms, a plaintext that is repetitive will result in a repetitive ciphertext?
An ingenious scheme that avoids many of the problems of symmetric encryption was proposed in 1976 by Stanford professor Martin Hellman and his graduate student Whitfield Diffie?
One of the most commonly used public-key algorithms is the 22-year-old RSA, named for its creators, Ronald Rivest, Adi Shamir, and Leonard Adleman of the Massachusetts Institute of Technology, Cambridge?
By far the most popular public-key encryption scheme is PGP, which was created in 1991 by a programmer and activist named Philip Zimmermann as a means of protecting e-mail?
Encryption is a two-edged sword: it has honorable purposes, true, but it can also be used to conceal out-and-out criminality?
The proliferation of encryption has coincided with the explosive growth of the Internet?
Data Encryption Standard, or DES developed in the 1970s, is still popular, especially in the banking industry. It is a block cipher, meaning that it encodes text in fixed-bit blocks using a key whose length is also fixed in length?
The alternative, known as stream ciphers, encode the stream of data sequentially without segmenting it into blocks?
Cryptography should be considered for data that is sensitive or has a high value if it is vulnerable to unauthorized disclosure or undetected modification during transmission or while in storage?
Gentlemen do not read each other's mail?