  # Cryptography | Computer science | Computing | Khan Academy

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# Unit: Cryptography

## Ancient cryptography

Learn What is cryptography? (Opens a modal) The Caesar cipher (Opens a modal) Caesar Cipher Exploration (Opens a modal) Frequency Fingerprint Exploration (Opens a modal) Polyalphabetic cipher (Opens a modal) Polyalphabetic Exploration (Opens a modal) The one-time pad (Opens a modal) Perfect Secrecy Exploration (Opens a modal) Frequency stability property short film (Opens a modal) How uniform are you? (Opens a modal) The Enigma encryption machine (Opens a modal) Perfect secrecy (Opens a modal) Pseudorandom number generators (Opens a modal) Random Walk Exploration (Opens a modal)

## Ciphers

Learn Ciphers vs. codes (Opens a modal) Shift cipher (Opens a modal) XOR bitwise operation (Opens a modal) XOR and the one-time pad (Opens a modal) Feedback (Opens a modal) Practice Bitwise operators 7 questions Practice

## Cryptography challenge 101

Learn Introduction (Opens a modal) The discovery (Opens a modal) Clue #1 (Opens a modal) Clue #2 (Opens a modal) Clue #3 (Opens a modal) Clue #4 (Opens a modal) Checkpoint (Opens a modal) What's next? (Opens a modal) Practice Crypto checkpoint 1 7 questions Practice Crypto checkpoint 2 7 questions Practice Crypto checkpoint 3 7 questions Practice

## Modern cryptography

Learn The fundamental theorem of arithmetic (Opens a modal) Public key cryptography: What is it? (Opens a modal) The discrete logarithm problem (Opens a modal) Diffie-hellman key exchange (Opens a modal) RSA encryption: Step 1 (Opens a modal) RSA encryption: Step 2 (Opens a modal) RSA encryption: Step 3 (Opens a modal) Time Complexity (Exploration) (Opens a modal) Euler's totient function (Opens a modal) Euler Totient Exploration (Opens a modal) RSA encryption: Step 4 (Opens a modal) What should we learn next? (Opens a modal)

## Modular arithmetic

Learn What is modular arithmetic? (Opens a modal) Modulo Challenge (Opens a modal) Congruence modulo (Opens a modal) Equivalence relations (Opens a modal) The quotient remainder theorem (Opens a modal) Modular addition and subtraction (Opens a modal) Modulo Challenge (Addition and Subtraction) (Opens a modal) Modular multiplication (Opens a modal) Modular exponentiation (Opens a modal) Fast modular exponentiation (Opens a modal) Fast Modular Exponentiation (Opens a modal) Modular inverses (Opens a modal) The Euclidean Algorithm (Opens a modal) Practice Modulo operator 7 questions Practice Congruence relation 7 questions Practice Modular addition 7 questions Practice Modular multiplication 7 questions Practice

## Primality test

Learn Introduction (Opens a modal) Primality test challenge (Opens a modal) Trial division (Opens a modal) What is computer memory? (Opens a modal) Algorithmic efficiency (Opens a modal) Level 3: Challenge (Opens a modal) Sieve of Eratosthenes (Opens a modal) Level 4: Sieve of Eratosthenes (Opens a modal) Primality test with sieve (Opens a modal) Level 5: Trial division using sieve (Opens a modal) The prime number theorem (Opens a modal) Prime density spiral (Opens a modal) Prime Gaps (Opens a modal) Time space tradeoff (Opens a modal) Summary (what's next?) (Opens a modal)

## Randomized algorithms

Learn Randomized algorithms (intro) (Opens a modal) Conditional probability explained visually (Opens a modal) Guess the coin (Opens a modal) Random primality test (warm up) (Opens a modal) Level 9: Trial Division vs Random Division (Opens a modal) Fermat's little theorem (Opens a modal) Fermat primality test (Opens a modal) Level 10: Fermat Primality Test (Opens a modal)

### About this unit

How have humans protected their secret messages through history? What has changed today?

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## Cryptography Tutorial - Tutorialspoint Definition: Cryptography is associated with the process of converting ordinary plain text into unintelligible text and vice-versa. It is a method of storing and transmitting data in a particular form so that only those for whom it is intended can read and process it. Cryptography | Computer science | Computing | Khan Academy Cryptography is used in all fields to secure data and prevent it from getting hacked. For example, for securing passwords, authenticating banking transactions, etc. Nowadays, various new cryptographic techniques are developed and cracked; hence, it is important always to be aware of computer threats and take precautions to avoid them as best as we can. What is Cryptography? Definition of Cryptography ... Cryptography is the science of using mathematics to encrypt and decrypt data. Cryptography enables you to store sensitive information or transmit it across insecure networks so that it cannot be read by anyone except the intended recipient. Cryptography Techniques | Learn Main Types Of Cryptography ... This is called 'decryption.' Cryptography begins when we abandon physical locks and use 'ciphers' instead. Think of [ciphers] as virtual locks. Ciphers allow Alice and Bob to scramble and descramble their messages so that they would appear meaningless if Eve intercepted them. Cryptography has been around for thousands of years. Cryptography - SlideShare Cryptography is the study of secure communications techniques that allow only the sender and intended recipient of a message to view its contents. The term is derived from the Greek word kryptos ... cryptography · PyPI This tutorial covers the basics of the science of cryptography. It explains how programmers and network professionals can use cryptography to maintain the privacy of computer data. Starting with the origins of cryptography, it moves on to explain cryptosystems, various traditional and modern ciphers, public key encryption, data integration, message authentication, and digital signatures. Real Life Applications of CRYPTOGRAPHY | by Prashanth ... Block Cipher. An encryption method that applies a deterministic algorithm along with a symmetric key to encrypt a block of text, rather than encrypting one bit at a time as in stream ciphers. Example: A common block cipher, AES, encrypts 128-bit blocks with a key of predetermined length: 128, 192, or 256 bits. Cryptography and its Types - GeeksforGeeks cryptography is a package which provides cryptographic recipes and primitives to Python developers. Our goal is for it to be your “cryptographic standard library”. It supports Python 3.6+ and PyPy3 7.2+. cryptography includes both high level recipes and low level interfaces to common cryptographic algorithms such as symmetric ciphers, message ... What is cryptography? (video) | Cryptography | Khan Academy Cryptography is technique of securing information and communications through use of codes so that only those person for whom the information is intended can understand it and process it. Thus preventing unauthorized access to information. What is Cryptography? | Cryptographic Algorithms | Types ... Unit: Cryptography. Lessons. Ancient cryptography. Learn. What is cryptography? (Opens a modal) The Caesar cipher (Opens a modal) Caesar Cipher Exploration (Opens a modal) Frequency Fingerprint Exploration (Opens a modal) Polyalphabetic cipher (Opens a modal) Polyalphabetic Exploration (Opens a modal)   