AP Computer Science Principles Digital Information

Caesar Cipher

A technique for encryption that shifts the alphabet by some number of characters

Cipher

a way of secretly writing or changing a message so that only someone who knows the secret method can understand it. It’s like a code used to hide information.

Cracking Encryption

When you attempt to decode a secret message without knowing all the specifics of the cipher

encode

to turn a message into a secret or special format so it can be stored, sent, or understood in a certain way

Decode

to change a secret or special message back into normal language so it can be understood.

Decryption

A process that reverses encryption, taking a secret message and reproducing the original plain text

Encryption

A process of encoding messages to keep them secret, so only "authorized" parties can read it.

Asymmetric Encryption

a way to lock and unlock messages using two different keys:

• A public key (shared with anyone) to lock the message.

• A private key (kept secret) to unlock the message.

Private Key

a secret code that only the owner knows. It is used to unlock or decrypt messages in asymmetric encryption.

Public Key Encryption

a way to lock messages using a public key that anyone can see and use. But only the person with the private key can unlock it and read the message.

cryptography

the science of protecting information by transforming it into a secure format

symmetric encryption

where the same key is used to encrypt and decrypt the message

bit

A contraction of "Binary Digit". A bit is the single unit of information in a computer, typically represented as a 0 or 1.

Byte

A group of eight bits.

ASCII

a code for representing English characters as numbers, with each letter assigned a number from 0 to 127

Pixel

Short for "picture element" it is the fundamental unit of a digital image, typically a tiny square or dot which contains a single point of color of a larger image.

Hexidecimal

A base-16 number system that uses sixteen distinct symbols 0-9 and A-F to represent numbers from 0 to 15.

Lossy

data that has been compressed in a way that loses some details. This means that after it's reduced in size, some of the original information can’t be recovered.

Lossless

Compressing data in a way that preserves all data away and allows full recovery of the original.