Questions About Cryptography

Encryption encodes standard language so only intended recipients can decipher it.

Cryptography is the science of transcribing and sharing messages in secret code. Many experts date the practice back to 1900 B.C. in ancient Egypt, shortly after the advent of writing, when a scribe used non-standard hieroglyphs to transcribe a message. Successfully communicating an encrypted message requires encryption, or the transformation from standard language to secret code, as well as decryption, or the conversion from secret code to standard language using a "key." Cryptography is widely used in Internet communications to send secure messages over unsecured networks.

Goals of Cryptography

In order for cryptography to function as intended, it must accomplish four things: authentication, privacy, integrity and non-repudiation. Authentication establishes the identity of both the sender and the recipient. In most Internet applications today this is either name or address-based, but both very weak security-wise. Privacy means that only the intended recipient can read the message. Integrity means ensuring that the message sent from the sender is the same read by the recipient. Non-repudiation confirms that the alleged sender, not someone else under her alias, really sent this information. Cryptography was developed and has evolved to accomplish these four objectives when sending information.

Types of Cryptography

Cryptography uses mathematical algorithms to create three types of encoded messages. Single Key Cryptography uses the same key shared by the message writer and reader to encode and decode standard language messages. Public key, or asymmetric cryptography, uses two separate keys: one for encryption and another for decryption. Lastly, hash-function cryptography uses no keys because the messages are not designed to be converted back to standard language test, and are used by computers as a "digital fingerprint" to authenticate users and establish the integrity of the message.

Keys

The critical component of successful encryption is protection of the decryption key. Keys use algorithms containing numbers so large that they are impossible to guess, and an exhaustive search is impractical. In some cases, message authors will provide a multi-part key, distributed to two or more trusted users who must combine this information to decipher the message, essentially doubling or tripling the level of complexity.

Crytography Strength

More complex and longer cryptography keys do not automatically equal increased security. The success of encrypted messages relies solely on the management and application of encryption keys. Theoretically, longer keys will resist attack better than shorter keys, but any key can be deciphered if enough time and computing power is devoted to it. Physically exchanging cryptography keys in person and using a secured network are the only ways to guarantee encryption security.

References

• Crytography World: The Cryptography Introduction and Guide
• Gary Kessler.net: An Overview of Cryptography