Flashcards
Compression, Encryption, & Hashing
Flashcards do conjunto (13)
- 1What is Compression and its 2 Types?> An algorithm which helps to reduce the size of files
> Useful to reduce space taken up in secondary storage, or to make sending the file quicker over a network
> Two types: lossy and lossless - 2What is the Difference between Lossy and Lossless Compression?> Lossy - removes unnecessary detail; some data is permanently lost, but enough remains so the file is still useful
> Lossless - none of the original data is lost; an algorithm is used to perfectly restore the original file. This is useful for text or executable files, where all the data is necessary
> Lossy reduces the file size more than lossless - 3What is Run-Length Encoding?> Form of lossless compression that replaces repeating sequences with more efficient representations
> Each repeating string is replaced by a code, which represents the section that repeats, and the amount of times it is to be repeated
> For example, AAABBCCCC becomes 3A2B4C
> This is useful in images, as adjacent pixels are likely to be the same colour - 4What is Dictionary (En)coding?> Useful for text files
> Each word is replaced by a binary number, which represents the word
> A dictionary stores which number represents which word
> Both the dictionary and the string of binary numbers are stored
> Sometimes, pre-existing dictionaries may be used to encode the text - 5What are the Advantages of Dictionary (En)coding?> Takes less bits to store a small binary number than a long word
> No data is lost (i.e., lossless compression)
> Pre-existing dictionaries can be used, meaning the algorithm can quickly encode the data - 6What is Encryption?> Process of scrambling data so that is cannot be read by third parties
> Done so by using a specific algorithm
> Only the intended recipient should know how to decode the data - 7What is a Key in Encryption?> A pair of very large prime numbers, usually 256 or 1,024 bits long, that the encryption algorithm depends upon to encrypt / decrypt data
> It would take an impractical amount of time to guess the key - 8Why is Encryption Important in Wireless Communication?> Wireless information can be intercepted by anyone, unlike wired communication, which requires a physical connection
> Wireless protocols, such as WPA2, encrypt all traffic to prevent this - 9What is Symmetric Encryption?> The same key is used to encrypt and decrypt data
> This encryption is usually done via a cypher algorithm
> Both the encrypted data and private key is transferred - 10What is the Problem with Symmetric Encryption?> Anyone with the key can decrypt the data
> The key could be intercepted to decrypt the data - 11What is Asymmetric Encryption?> Uses two keys: a public key and a private key, related to each other through mathematical operations
> The public key is given to the sender by the recipient
> This public key is one-way, i.e., it can only encrypt and not decrypt the data
> The private key can decrypt the data previously encrypted by the public key. This must never be shared. - 12What is Hashing?> Process of taking an input, performing some algorithm / calculation on the input, and outputting a value of fixed size
> The output is known as a hash
> Hashing algorithms are non-invertible, meaning you cannot reverse a hash and get back to the original data - 13How can Hashing be used to Store Passwords?> The password is put through a hashing function, and stored as the encrypted password
> Password attempts are entered, but only the same password will output the same output of the hashing function
> No one can know the password just by looking in the database where it is stored
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- A level Computer Science (Compression, Encryption, & Hashing) FlashCards sobre Compression, Encryption, & Hashing, criado por Malachy Moran-Tun em 06-12-2022.
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- Malachy Moran-Tun
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- Criado por Malachy Moran-Tun · 6 dez 2022
- Copiado por Malachy Moran-Tun · 6 dez 2022
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