key - technical definition

Cryptography is the act of securing information by encrypting it, and cryptanalysis is the act of decrypting encrypted data to make a message intelligible. Cryptology is the area of mathematics that includes both cryptography and cryptanalysis.

Modern cryptography uses algorithms, or complex mathematical equations, and secret keys to decrypt and encrypt information. A key is a number or a string that is typically fewer than 20 characters. Symmetric keys use the same key for decryption and encryption, whereas asymmetric keys are produced in pairs—one key encrypts the information and the other, “mirrored” key decrypts it. Thus, someone having only one key could not figure out the other key.

A common question in security pertains to differences between 40-bit and 128-bit encryption in Internet browsers. The easiest way to break encryption in order to read the plaintext is simply to try all possible keys. To help indicate the relative degree of difficulty in carrying out this task, it is important to realize that a 40-bit key has one trillion combinations. So, it would take a lone computer many weeks to attempt all these combinations. A cracker with considerable time on his or her hands would likely need just a few weeks to decrypt a message sent across the Internet with a 40-bit browser.

Furthermore, every increase in key length means that the key will take double the time to crack. For argument’s sake, if a computer needs one week to crack a 40-bit key, it will take twice as long to break a 41-bit key—and for a 128-bit key, it will need an estimated 309,485,009,821,345,068,724,781,056 times longer to break it.

See Also: Cryptography or “Crypto”; Decryption or Decipher; Encryption or Encipher.