oakley sunglasses encrypted with the Caesar dense sheet is equivalent to the modulus 26 plus 3

They transformed the relationship between each other inverse transformation. In other words, expressly one of the transform encryption to produce ciphertext, then another to transform this ciphertext to be decrypted, it will get the original plaintext. This mutual inverse relationship as the inverse operation of addition and subtraction we know each other: coupled with a number and then subtract the same number, it means that without also diminished. (Later we will know, encrypted with the Caesar dense sheet is equivalent to the modulus 26 plus 3, and use it to decrypt the equivalent modulus 26 minus 3)
Secret key
We see that the transformation rules of the password is obviously critical. A transformation rule once the enemy's grasp,oakley sunglasses, all communications are encrypted with this rule will be no secret at all. Therefore, the transformation rules must be kept strictly confidential and password security and the security of transformation rules, there is a To improve password security to prevent the enemy easily deciphered, we should transform the rules as possible, for example, not with letters instead of letters, but instead of groups of letters with the letter group; complex transformation rules to a certain extent, becomes difficult to remember; and difficult to remember words it recorded for future reference; - there are written records of its security compromised. First, the record of this text at least to the communicating parties have, so there are multiple copies, more copies of the worse of the security; such written records custodians may be separated, which increased by others steal the possibility of replication; transformation rules need to be changed frequently, so it must send a new text record, but both the artificial transmission of ancient or modern electronic transmission is obviously very insecure.
Method is to break the derivation (Group) As the name suggests, the key is the key to open the lock passwords.
For example, the the Caesar secret key of the table is dense table of the specific content. If it is a huge secret table (such as the Chinese telegraph code book), and relatively short key, then you have to take the confidentiality of this dense table for a lot of effort. Although this password in practice been used, but generally only used to have a relatively fixed latency location and camouflage to get better intelligence, greater mobility of military operations department, this password is not desirable . Therefore, in the military cryptography,cheap oakley sunglasses, we consider only the short key password.
I said before, the encryption transform and decryption of two mutually inverse transform transform in a few decades ago, this distinction is generally not very stressed, as long as know one of transformation, its inverse transformation is at hand. But by the 1970s, this concept was to break the Kind of transform, transform into another state - state transform its calculation is very easy; in turn, transform back to the original state from another state, that is, the inverse transformation, although in theory