A Survey of Digital Signature Schemes
Cryptography, in the computer context, is the act of storing information in a form which allows it to be revealed to those who have a need or a right to see it, while at the same time hiding it from all of those who have no right or need to see it. The state of the art method of accomplishing this today is by the use of a coherent "crypto system" which includes both encryption (cryptography) and decryption (cryptoanalysis). In both of these aspects, we are concerned with the original information -- referred to as "plaintext". When this plaintext is converted into hidden ciphers, then the text becomes known as "ciphertext."
The act of converting plain text into ciphertext is known as "encryption" and it works like this. Let us assume that we have the following plaintext message:
The simplest form of encryption would be to substitute a number for a letter using a basic number table.
Using this kind of grid, A = 11, B=21, U=33 and so on (Edwards, 2001; Shimover & Ball, 2002).
Using this system, "Good/ Morning/ America" would become
"71 62 62 41/ 42 62 92 52 91 52 62 11 42 51 92 91 31 11" When the phrase "Good Morning America" is encrypted in this example to "716262414262925291526211425192913111" the coded string is known as "ciphertext". This ciphertext could then be sent as an electronic signal to another computer that would know to "decrypt" or "decipher" using the number table that we have just seen. Encryption is any procedure to convert plaintext into ciphertext. Decryption is any procedure to convert ciphertext into plaintext."
Cryptosystems, such as those that will be surveyed in this analysis, are all designed to control the situations under which decryption can be accomplished. Keep in mind, however, that the same system described above, that of simple alpha numeric substitution, is used in all systems (Kideki & Hartmanis, 1998; Schneier, 1995).
The compl...