Encryption Technology Basics

All encryption is performed via some kind of mathematical conversion process:

4 Steps to Decrypting Data

Determine the language used of the clear text. (English [ASCII], Japanese [JIS, S-JIS, EUC], Machine Language, 1-bit/1-byte database fields, DOC, XLS, PPT, JPG, etc.)
(This assists in determining the easiest method to break a coded message.)
Determine the encryption method used.
(Decryption is the reverse process of encryption, know the encryption method and you can start by using the proper decryption method.)
Find or create the Key or Code Book used to encrypt the message, once found, use the discovered Key or Code Book and decryption method to decrypt the data.
Depending on the encryption method this could be very easy or virtually impossible to break!
Look for recursive/repetitive patterns. All known languages have them.
By properly intermixing random garbage during encryption can hide these recursive/repetitive patterns such that cryptanalysis becomes virtually meaningless.

Most Common Attack Methods

cipher text-only: Create a key from the encrypted text.

known-plain text: Perform cryptanalysis using all or a portion of the clear text.

chosen-plain text: By knowing which portion of clear text encrypts to which coded data.

chosen-cipher text: Finding the key without even knowing the clear text. (RSA Public Key Method)

Key to the Security Mystery Top

Most Common Attack Methods
cipher text-only:	Create a key from the encrypted text.
known-plain text:	Perform cryptanalysis using all or a portion of the clear text.
chosen-plain text:	By knowing which portion of clear text encrypts to which coded data.
chosen-cipher text:	Finding the key without even knowing the clear text. (RSA Public Key Method)