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1.3.1a: Lossy vs Lossless compression.
Keyword
Definition
Compression ratio
The ratio of the size of the original data to the size of the compressed data, which is a measure of the effectiveness or the efficiency of a data compression algorithm or a data compression technique.
Data compression
The process of reducing the size of a data file or a data stream in order to save storage space, reduce transmission times, or improve performance.
Lossless compression
A type of data compression that preserves all of the information or the quality of the data, but achieves a lower compression ratio, and that is typically used for compressing text, binary, or executable data.
Lossy compression
A type of data compression that sacrifices some of the information or the quality of the data in order to achieve a higher compression ratio, and that is typically used for compressing audio, video, or image data.
Redundancy
The property of a data file or a data stream that contains repeating or correlated information, or that contains information that can be predicted or inferred from other information, without affecting the meaning or quality of the data
1.3.1b: Run length encoding and dictionary coding for lossless compression.
Keyword
Definition
Dictionary coding
A lossless data compression technique that uses a codebook to encode the data file or the data stream, and that replaces the original data with a sequence of tokens or codes that represent the data in a more compact or more efficient form.
Lossless compression
A type of data compression that preserves all of the information or the quality of the data and that is typically used for compressing text, binary, or executable data.
Run-length encoding
A lossless data compression technique that uses the repeated values or the repeated patterns in a data file or a data stream to reduce the size of the data by replacing a sequence of identical values or patterns with a single token or code that specifies the value or the pattern, and the number of repetitions or the length of the sequence.
1.3.1c: Symmetric and asymmetric encryption.
Keyword
Definition
Asymmetric encryption
A method of encryption that uses public and private keys to encrypt or decrypt data without needing a shared password
Ciphertext
a message that can only be read with a password
Decoding
using an algorithm to represent data back into its original form without needing a secret or password
Decryption
an algorithm that uses a secret in order to convert a ciphertext message back into a plaintext message
Encoding
using an algorithm that represents data in a different form without using a secret or password
Encryption
an algorithm that uses a secret in order to convert a plaintext message into a ciphertext message
Plaintext
a message that is readable without needing a password
Symmetric encryption
A type of encryption which requires a password to be shared before data can be decrypted
