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Lecture# Introduction to Cryptography: Basics and Techniques

Description

This lecture covers the basics of cryptography, including the one-time pad, perfect secrecy, and public-key cryptography. It explains the importance of privacy and authenticity in communication, the historical context of cryptography, and various encryption techniques. The instructor discusses the fundamental concepts of plaintext, ciphertext, keys, encryption, and decryption. The lecture also delves into ancient ciphers like Caesar's cipher, monoalphabetic ciphers, and polyalphabetic ciphers. It explores the concept of perfect secrecy and the vulnerabilities of different cryptosystems. The one-time pad is highlighted as a secure encryption method, emphasizing the significance of high-entropy keys for achieving perfect secrecy.

Official source

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In course

COM-102: Advanced information, computation, communication II

Text, sound, and images are examples of information sources stored in our computers and/or communicated over the Internet. How do we measure, compress, and protect the informatin they contain?

Instructor

Related concepts (60)

Vigenère cipher

The Vigenère cipher (viʒnɛːʁ) is a method of encrypting alphabetic text where each letter of the plaintext is encoded with a different Caesar cipher, whose increment is determined by the corresponding letter of another text, the key. For example, if the plaintext is attacking tonight and the key is OCULORHINOLARINGOLOGY, then the first letter a of the plaintext is shifted by 14 positions in the alphabet (because the first letter O of the key is the 14th letter of the alphabet, counting from 0), yielding o; the second letter t is shifted by 2 (because the second letter C of the key means 2) yielding v; the third letter t is shifted by 20 (U) yielding n, with wrap-around; and so on; yielding the message ovnlqbpvt eoeqtnh.

Ciphertext

In cryptography, ciphertext or cyphertext is the result of encryption performed on plaintext using an algorithm, called a cipher. Ciphertext is also known as encrypted or encoded information because it contains a form of the original plaintext that is unreadable by a human or computer without the proper cipher to decrypt it. This process prevents the loss of sensitive information via hacking. Decryption, the inverse of encryption, is the process of turning ciphertext into readable plaintext.

Substitution cipher

In cryptography, a substitution cipher is a method of encrypting in which units of plaintext are replaced with the ciphertext, in a defined manner, with the help of a key; the "units" may be single letters (the most common), pairs of letters, triplets of letters, mixtures of the above, and so forth. The receiver deciphers the text by performing the inverse substitution process to extract the original message. Substitution ciphers can be compared with transposition ciphers.

Key (cryptography)

A key in cryptography is a piece of information, usually a string of numbers or letters that are stored in a file, which, when processed through a cryptographic algorithm, can encode or decode cryptographic data. Based on the used method, the key can be different sizes and varieties, but in all cases, the strength of the encryption relies on the security of the key being maintained. A key's security strength is dependent on its algorithm, the size of the key, the generation of the key, and the process of key exchange.

Encryption

In cryptography, encryption is the process of encoding information. This process converts the original representation of the information, known as plaintext, into an alternative form known as ciphertext. Ideally, only authorized parties can decipher a ciphertext back to plaintext and access the original information. Encryption does not itself prevent interference but denies the intelligible content to a would-be interceptor. For technical reasons, an encryption scheme usually uses a pseudo-random encryption key generated by an algorithm.

Related lectures (70)

Cryptography Basics: Symmetric and Asymmetric EncryptionCOM-402: Information security and privacy

Introduces the fundamentals of cryptography, focusing on symmetric and asymmetric encryption, data integrity, authentication, and non-repudiation.

Perfect Secrecy: One-time PadCOM-102: Advanced information, computation, communication II

Explores perfect secrecy, the one-time pad encryption method, attacks on encryption systems, and the Vigenère cipher.

Ancient Cryptography: Security and Information TheoryCOM-401: Cryptography and security

Explores ancient cryptography, key security, perfect secrecy, and the Shannon encryption model.

Applied Cryptography: Symmetric Encryption and Hash FunctionsCOM-301: Computer security and privacy

Introduces symmetric encryption, hash functions, and their practical applications in cryptography.