1.3.1 - compression, encryption and hashing Flashcards
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compression
The process of making a file smaller/ take up less storage.
lossy compression
When unrequired data is removed from a file. Loss of quality but significantly smaller file size
lossless compression
When data in a file is stored in a different format.
two types of lossless compression
- run length encoding (RLE)
- dictionary
run length encoding
Colour of pixel followed by number of pixels.
dictionary based compression
encryption
The transformation of data from one form to another to prevent an unauthorised third party from being able to understand it.
symmetric (private key) encryption
Uses the same key to encrypt and decrypt data. This means that the key must also be exchanged to the same
destination as the ciphertext, which can be intercepted.
asymmetric (public key) encryption
- Uses 2 separate, but related keys.
- Senders can use your public key to encrypt messages.
- Only the recipient’s private key can decrypt this.
- The message can be digitally ‘signed’ to authenticate the sender.
hashing
- A result generated by applying an algorithm to a value.
- Usually fixed length or
smaller output. - One-way
3 uses of hashing
- storing passwords
- searching a database
- digital signatures
4 purposes of compression
- reduce size of files
- reduce download times
- reduce storage requirements
- make best use of bandwidth
Caesar cipher
Replaces each letter of the alphabet with another letter, a fixed distance away from the original letter.
primary key
A field which which has a unique value for each record.
List 2 important features of a hashing algorithm. (2)
- low chance of collision
- smaller output than input
