1.3.1 Compression, Encryption, Hashing

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loseless compression

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reduces the file size that when it is decompresses all the data is retrieved. does this by recording patterns in the data rather than the actual data.

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use of lossless

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code, text, architercural plans

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27 Terms

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loseless compression

reduces the file size that when it is decompresses all the data is retrieved. does this by recording patterns in the data rather than the actual data.

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use of lossless

code, text, architercural plans

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lossy compression

removes all non-essential data. reduces a file size such that when decompressed some data is lost

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use of lossy

colour depth reduction, resolution reduction

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example of lossy compression

MP3 format file is 10% smaller than original, quiet sounds and high frequencies are cut out

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2 examples of lossy compression

voice transmission, mp3

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run length encoding and dictionary encoding are 2 types of …

lossless compression

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run length encoding

compression where data is stored as frequency data pairs.

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what is compression?

the process of reducing space needed to store a file

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what is a frequency data pair?

single instance of a pattern and how many repetitions of the pattern

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con of dictionary encoding

not useful for smaller bodies of text as it requires text in dictionary to be stored.

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con of RLE

doesn’t work well for Digital images because the repetitions aren’t frequent.

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plaintext

the original data

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ciphertext

encrypted data

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cipher

encryption method

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key

information needed to lock or unlock the data

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encryption

transformation of data from plaintext to cipher text to protect sensitive data

encryption is two-ways meaning that data can be resorted into its original form, still requires and encryption key.

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symmetric encryption

private key

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conditions of symmetric encryption

same key used to encrypt and decrypt text

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cons of symmetric encryption

less secure key exchange means that high likelihood that any interception leads to cipher text being decrypted.

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conditions for asymmetric encryption

uses two separate and indistinguishable keys; public key for encryption; private key to decrypt.

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What is the purpose of compression

Reduce size, download time and storage requirements. Make best use of the bandwidth.

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what is a hashing algorithm?

a mathematical function that garbles data and makes it unreadable. used in data storage and security for protecting sensitive information.

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what are 2 key properties of hashing algorithms ?

consistency-same input produces the same hash. sensitivity - minor changes produce completely different hash

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Name three common hashing algorithms

MD5 SHA-1 SHA-256

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What are the characteristics of a good hash?

Easy to calculate, few collisions and provides an output smaller than the input.

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what is hashing?

hashing is a one-way non-reversible mathematical process that produced an value from the input value