Compression, Encryption and hashing
Define 'Sampling'
At a given time point in a sound, a measurement is taken
Give the formula for the size of the sampled resolution
Sampling rate(no of bits) x sample resolution x length of the sound(seconds)
Define 'Compression' and give the two types of compression
The process of reducing a file's size.
Lossy compression
Lossless compression
Give two benefits of compression
- Reduces file size
- Files are quicker to be transferred
What does 'Lossy compression' and name files where it is used on
Reduces file size by permanently removing data from the file.
JPEG
MP3
MPEG-1
MPEG-2
What does 'Lossless comprssion' do and give examples of where it is used
Reduces the size of the file however doesn't remove data from the file.
PNG
ZIP
GIF
Give 2 ways of reducing file size of an image
- Store a lower number of colours
- Store a larger area of pixels as a single colour
Name 2 types of lossless compression
Dictionary coding
Run-length encoding
What does 'Dictionary coding' do
Replaces recurring sequences with shorter unique codes
Where would dictionary coding be useful and where would it not be useful?
Useful: Large text documents with repeating data
Not Useful: text documents with no repeating data, takes up more space
What does 'Run-Length encoding ' do
Condenses identical data into single values with a count
Where would you use run-length encoding?
In bitmap images. Where you have contiguous pixels of the same colour so you store the binary for one of the pixels and multiply it by the number of pixels with that colour
What is the purpose of encryption?
To make the original code impossible to crack without the key
What is the difference between Cipher and Plain text
Plain text - text that is reabdable by anyone
Cipher text - text that can only be read by someone with a decryption key
What is 'Symmetric encryption' and give some drawbacks of it
Where a single key is used to both encrypt and decrypt a message.
- Messages can be cracked by someone intercepting the key
- Messages can be crakced by someone duplicating the production of the key to get a copy
What is 'Asymmetric Encryption'
Where the key used to encrypt the message (public key) is different to the key needed to decrypt (private key) the message (key pair)
Give benefits of 'Asymmetric encryption'
- The sender and recipient are sure no one else can read their message
- You're sure the message hasn't been modified
- You can be sure the message is authentic
How does asymmetric encryption work
The sender gives the recipient their public key. The recipient uses the public key to encrypt a message and send back to the sender. The sender then uses their private key to decrypt the message
Where would you use symmetric and asymmetric encryption
Symmetric: On large files and databases
Asymmetric: Confidential data
Define 'Hashing'
Transforms a string into a fixed length value or a key that represents the input string
Give 2 common hashing algorithms
MDA
SHA-1
SHA-256
SHA-3
Define a 'hash table'
A data structure used to remove & insert key value pairs
What makes hashing a different process to encryption
Hashing is a one-way process, meaning you can't get the original value from the hashed value even if you have the hashing algorithm
Why do hash tables need to be large in size
In order to reduce the chance of a collision occurring
Define a "Collision"
Where two different inputs produce the same hashed value
Give 3 features of a good hashing function
- Be calculated quickly
- Result in as little collisions as possible
- Use as little memory as possible
Define "Open Addressing"
A process which searches for the next available empty space in a hash table and stores the item there.
Define "Linear probing"
Searching for an empty spot by checking the next slot sequentially
Give 2 disadvantages of "linear probing"
- It prevents certain items being stroed in their correct location
- Can cause clustering
Define "Clustering"
Where many inputs have the same hashed value or similar hashed values causing large blocks of occupied slots, which increases search time (reduces efficiency)
Give another way of handling collisions
2D hash tables, this can allow more than one item to be placed in the same index (chaining)
Give a 3rd way of handling collisions
Overflow tables, a second table used to handle collisions when the first table is either full or items can't fit in their expected location
| Quiz |
|---|
| Gravitational Fields |
| verbs |
| CM5 : La bio faconné par l'environnement biotique et abiotique |
| patrick do my hoework |
| giada |
| historia 3 |
| Spanisch Vocablen |
| VALENCIAS ELEMNTOS |
| EXAMEN 1 JUSTIFICADAS |
| giada |
| Biologie |
| Medicina interna |
| Nask 2.2 tm 2.6Hier is alles in een korte, overzichtelijke tekst:
1. Kleurenspectrum: Het kleurenspectrum zijn alle kleuren in wit licht, zoals in een regenboog.
2. Lichtbronnen: Een lichtbron geeft zelf licht, z... |
| last minute |
| English Nri quiz 5 |
| logstiek |
| Medicina interna - RUBI |
| Tema 17 汉语 Red |
| 2 reproductive system |
| part 2 central nevoisss |
| forragemGênero Cynodon:
❖ Alta produtividade e elevado valor nutritivo
❖ Boa cobertura e conservação do solo
Espécies
Principal característica de diferenciação
Grama-bermuda C. dactylon
❖ Apresenta rizomas
❖ ... |
| cranial nerves |
| electricity exam |
| protien synthesis & cell structure |
| exam reproduction |
| diff imper/per |
| افشاریه |
| nervous system |
| imper/per |
| cos tan sen |
| bio cell |
| 1er parcial |
| medicina interna pruebas - copia |
| BoP equations |
| anatomi |
| spanish flash cards |
| Vocabulaire Art & Pouvoir |
| vocabulario geografiahlk |
| Prueba 2 |
| Tyska glosor |
| Il Sistema Muscolare |
| glosor V.50 |
| Eval PC 3 |
| 21st |
| Chapter 12chapter 12 |
| scheikunde elementen - invullen |
| mathe |
| scheikunde elementen - MeerkeuzeElementen van dat ene blaadje |
| GH II |
| naoki |
| Liste des radicaux |
| diritto |
| texte 2 |
| duits |
| HEPSY |
| 漢字 Lesson 11MNN Basic Kanji Book. |
| CRPT 409 |
| FalaciasPara el examen |
| Characters |
| pourcentage |
| pEbadminton |
| CONTINUITE |
| LIMITES |
| Learn them |
| prueba recuperativa |
| CRPT 410 |
| UE 6 TESTING MAIN |
| Verderb duch VorratsschädlingeTest |
| zodziiai |
| Prueba 1 |
| medicina interna pruebas |
| Prueba recuperativa |
| voc anglais |
| Sensitive Skin & Health Challenged Skin |
| relieve de europa |
| Sun Damage |
| filkom |
| Patología respiratoria |
| Duits Schritt 51 |
| maths |
| so begrep |
| APPLICATIONS |
| The church and its invlovement in medicine |
| svenska |
| economics continued |
| Farm animals |
| Learn with us 2Farm animals |
| vocabulary unit 1,2,3 |
| economics |
| voc |
| Laentha Saoire |
| Medieval Surgery |
| UE 6 GONIO EPAULE |
| Französisch Voka Unit 2 |
| Hippocrates and Galen |
| 50 |
| wunder aufbau jesus |
| wunder jesus arten |
| frauen im neuen Testament |
| frauen im alten Testament |
| hoheitstitel jesus messias herr gottessohn |
| wirtschaft |
| mavo |
| wunder jesus |
| hoheitstitel jesus Bedeutung |
| Muskler |
| Mikrobiologischer VerderbTest |
| Pistenskilauf negative Auswirkungen in alpen und folgen |
| Massentourismussyndrom |
| Alternativkonzepte alpen |
| Auswirkungen des Fremdenverkehrs auf die Wirtschafts-, Sozial- und Raumstruktur |
| Topographie Alpen |
| bergbauern in den Alpen |
| bergwald in den Alpen funktion |
| ph wert chemie |
| ph wert berechnen in wässriger Lösung |
| ph wert ausrechen mit Prolyten |
| Säure Base Theorie nach Brönsted |
| LF3 Mikrobiologie |
| week 11 stress and the skin |
| Leder & terminologi |
| vocabulario |
| passé simple irrégulier + conjugaison |
| week 12 glycation |
| histoire Athènesla citoyenneté à Athènes à l'époque classique |
| Tiempos verbales |
| psychiatrie |
| Environnement Juridique |
| german words for Dec 12 |
| Revisons prepa |
| Vocablen |
| anglu 4 skyrius |
| Finals: ELEC |
| spanska |
| Vocabeln |
| know your computer |
| nidhi |
| UE 6 TESTING SCAPULO HUMÉRALE |
| jaimes dr |
| 𝐬𝐜𝐢𝐞𝐧𝐜𝐞𝐬 𝐟𝐨𝐫𝐦𝐮𝐥𝐞𝐬 |
| Belysningsstyrning och protokollGrunder i belysningsteknik - tenta del C |
| 𝐇𝐢𝐬𝐭𝐨𝐢𝐫𝐞 : 𝐥𝐞𝐬 𝐜𝐞𝐥𝐭𝐞𝐬 |
| les obits |
| Deva Nakshatra |
| admin |
| Parasitiods (Lec 3) |
| Philo racines latines |
| K.Mklassisk musikhistoria
barok
weinklassicism
romantik |
| obdachloss helfen |
| Philo racines grecques |
| Mass Production (Lec. 4) |
| Prov anatomi |
| Biological Control (Lec. 5) |
| gestion |
| entertainment |
| history |
| Kemia koe |
| cirugia |
| MARKETING 4+5+6 |
| Prov - Religion |
| هنرمندان صفوی |
| Bio Quiz (Living things, cell organelles, mitosis) (gr 10 science) |
| Triads! (gr 10 music) |
| Capitals quizcapitals of the countries for the human geog exam |
| fisica |
| stofwisseling............................... |
| Sosgtest |
| Classification des tissus |
| Patología cardíaca- hepática veterinaria |
| Ein Mann Seiner Klasse |
| Chapter 29 |
| Questões objetivas |
| collapse of weimar |
| final oral |
| les cristaux |
| ENSEMBLES |
| BIOLOGI |
| Europa |
| The Canturbary Tales - Vocabulary |
| GarungTest |
| TEMA 1 Mecanica clasica |
| gloceu |
| andra världskriget o mellankrigstiden åk9 |
| De sluwe avondturier 2 sloten buiten editie |
| English Exam - Child Language |
| frans |
| De sluwe avonturier 1 slot buiten editieKraak het slot! |
| kemi |
| une structure complex la cellule |
| français |
| istorija LDK |
| medier |
| latina slovicka 4. lekce |
| ital prüfung |
| Questões objetivas |
| scienze. |
| Examen |
| espagnol |
| De verkennende avonturier - kopie |
| oral - copy |
| Sts 1 |
| oral |
| SUITESrien |
| lag och rätt |
| LebensmitteltechnologieTest |
| higiene del medio hospitalario y limpieza de material |
| cuidados auxiliares de enfermería |
| تفسير سورة البقرة ١-٥ |
| تفسير سورة الفاتحة |
| afrika |
| vocab |
| MICROBIOLOGYMicro bio lemar flashcards |
| Bw -GorgsKa |
| Polizia |
| ÖD |
| Neuro |
| Words and Phrases |
| molière et la classisisme |
| Mer utförliga svar |
| molière et le classisisme |
| Stress |
| biologisk psykologi |
| 223 | StGB |
| irregular verbs 5 |
| Drama tentaövning |
| FunktionsklassenVerbesserung meiner Mathekenntnisse |
| Literaturepochen, geg Literaturepochen |
| GEOGRAFÍAme encanta |
| PDHPE- Assessment Task 1 |
| anatomyn/a |
| evolution bio |
| Part 3 |
| soci final |
| cat |
| Passé composé (Pre-IB French 10) |
| PRUEBA RECUPERATIVA |
| Part 2Author of The Joy Luck Club, a novel about Chinese-American identity and generational conflict |
| PRUEBA 1PATOOO |
| biologia |
| biologia |
| unit 2 |
| språkistoria (epoker)svenska - språkhistoria (epoker + tendenser) |
| woordenschat 5 |
| gestion |
| connorCriminal Law Flash Cards answer the questions yes/no |
| Wr/ |
| UE15j |
| Hausa |
| english words |
| 11.3: Bezienswaardigheden |
| 11.2: Accomodatie |
| strategic management capitoli 1 a 4 |
| Franska prov |
| la epica |
| las jarchas y las cantigas de amigos |
| La lirica medieval |
| 11.1: Reizen en reisvoorbereidingen |
| Verbos |
| Skelettet |
| Vocabulario |
| Pragmatics |
