The Crypt

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Dictionary

Algorithm

Set of steps or instructions (usually mathematical) used to encrypt or decrypt.

Alice

See Bob

Bit

"Piece" of information. In most computers, a bit is a 1 or a 0.

Bob

Imaginary person, who, along with Alice and Eve, is often used to help discuss how secure communications take place. Usually, Bob and Alice wish to have a secure conversation over an insecure channel, and Eve is trying to intercept their conversation. NOTE: A news story I once read attributed Alice and Bob to quantum physicists. Not so, these just happened to be quantum physicists working on quantum cryptography

Channel

Method by which information is transmitted. Can either be secure or insecure.

Cipher

n. Part of crypto-system representing encrypted information. v.To encrypt into a cipher.

Cipher Text

See Cipher. Of course, you don't suppose this has anything to do with my domain name, hmm?

Code

Code, as used in cryptography, refers to a substitution encryption system where individual symbols or letters represent standard phrases or words.

Cryptographic System

Complete set of both unique encryption and decryption, includes various standards, methods, and usually mathematic proofs.

Cryptography

Making information hidden. In comparison to steganography, however, cryptography does not involve hiding the information itself, but changing it so that it is rendered incomprehensible to all but the intended parties.

Crypto-System

See Cryptographic System

Decrypt

To restore meaningless garbage into information, often (but not always) based on the exact reverse process that encrypted the information.

Encrypt

To change information to make it loose it's meaning without being deencrypted.

Eve

See Bob

Factor

To express a number in terms of smaller numbers multiplied together. IE, 15=3*5.

Key

Just like what it sounds; piece of information necessary to lock or unlock (encrypt or decrypt) information.

Number Theory

Study of properties of whole numbers. Field of mathematical study in which most cryptography is based.

PGP

Pretty Good Privacy; encryption system written by Phillip Zimmerman based on RSA.

Plain Text

Unencrypted message. The very beginning or very end of encryption and decryption.

Prime numbers

Numbers which can only be divided evenly by themself and 1. Primes are extremely important in cryptography. Also, see Unique Factorization Theorem.

Private Key

See Public Key Cryptography

Public Key Cryptography

Major breakthrough for cryptography. Instead of having the same key to encrypt and decrypt a message, public key cryptography uses a key-pair. A public key, and a private key. What one key does, only the other can undo. While simple sounding, this really is an amazing breakthrough. Because of this, it's not necessary to share a secret key at any point, which was and is the achilles heel of most other crypto-systems. They assume there is secure communication at some point where a method, or a code is shared. Public Key Cryptography needs no secure channel what so ever. In fact, the more public the communications channel is, the more likely the message will be secure.

Public Key

See Public Key Cryptography

Quantum Computers

(QC) Comptuers that take advantage of strange properties of quantum physics. To make a very very long story short, quantum physics is based on the idea that there are really wierd things that happen to very small particles if you don't look at them. They can in fact, be in infinitely wierd states at the same time. Quantum computers take advantage of this effect and are therefore not limited to just 0's and 1's, but any infinite number of possiblities, each with different probabilities. Does your head hurt? One of the leading quantum physcists once said that if you can think about quantum physics without hurting your head then you have no truly understood it. The is important in cryptography because quantum computers can factor large numbers very, very easily. Since this is the basis for Public Key Cryptography, it's a very important issue. If large-scale quantum computers are ever built, they will rip through current encryption like me going through a bag of skittles. Currently, the largest quantum computer is 7 qubits big.

Quantum Cryptography

Fortunately for cryprographers, the cryptanalyticly inclined don't automatically win if a QC is ever built. In fact, it looks like the code-makers might finally be able to put a stop to the long battle of making and breaking that codes (codes used in the generic sense here) have undergone throughout history. Already being worked on is the field of quantum cryptography which is so secure that it can be mathematically proven to be inviolate. Not only that, but even trying to listen in on the secure channel will disrupt communications, allowing Alice and Bob to know that Eve is trying to tap into their channel.

Qubit

Bits in a quantum computer. Not limited to 1 and 0, but can be an infinite number of possibilities.

RSA

First public-key crypto-system. Developed by Ronald Rivest, Adi Shamir, and Leonard Adleman in 1977.

Steganography

The study of making information hidden through obscuring the information itself. Hiding words inside pictures, adding a secret data track to a CD, hiding a message inside a full length book when letters at specific intervals are examined; these are all examples of steganography.

Substitution

By far the more powerful of the two main cryptographic systems, substitution involves replacing each bit of information (pun intended; it works both ways) with another bit based on some pattern or formula.

Transposition

A cryptographic system where information is rearranged, but not actually changed.

Unique Factorization Theorem

(Also known as the fundamental theorem of arithmetic) Important part of number theory that states that every whole number has a unique factorization if all factors are primes. In other words, there's one unique way to factor every number into the primes that compose it. 60=2*2*3*5. By UFT, 60 cannot be expressed with any other set of primes.