Reviewer - Lecture 1, 3, 4 PDF

Lecture 1 - Cipher Cryptography Cryptosystems - include the regulation of Diffusion - serves to spread the influence of human behaviors like choosing complicated the plaintext bits and the key bits over as...

Lecture 1 - Cipher Cryptography Cryptosystems - include the regulation of Diffusion - serves to spread the influence of human behaviors like choosing complicated the plaintext bits and the key bits over as much passwords and logging off unused systems. of the ciphertext as possible. Cryptographic algorithm - set of procedures Feistel network - used in many block ciphers that encrypt or decrypt messages to secure to ensure that the algorithm is invertible. computer system communications within == devices such as smartphones as well as Data Encryption System (DES) Encryption applications. Algorithm - Algorithms create a fixed length of == block ciphers with a secret key that the sender Symmetric Cryptography Algorithm uses to encipher data and the receiver uses to 1.Plaintext - is the original data / message that decipher data. Cryptography - the process of communicating Advanced Encryption Standard (AES) the algorithm uses as input. secretly through the use of ciphers, and 2.Encryption algorithm - The encryption Encryption Algorithm - the Rijndail algorithm cryptanalysis, the process of cracking or algorithm performs various mathematical that is capable of 256-bit (or more) key to deciphering such secret communications. A method of protecting communication and operations on this plaintext data to encrypt it. prevent hacker intrusions. information through the use of codes so that 3.Ciphertext - This is the scrambled message == only those who are meant to receive the that is the result of the encryption algorithm. If Cipher - method in which a message is information can read and process it. intercepted by an untrusted user, it is merely transformed to conceal its real meaning. seen as garbled data. Cipher algorithm - protocol embedded A set of calculations called algorithms that process involves private and public key 4.Secret Key - also input to the encryption transform hard to decipher messages: algorithm. The encrypted data / message is generation for data encryption/decryption, cryptographic key generating, digital signatures, and verifications. then sent to the end user, who uses the same digital signing, and verification for message secret key to decipher the data. authentication. == 5.Decryption Algorithm - It takes the == ENCRYPTION AND DECRYPTION ciphertext, the secret key, and produces the Reverse cipher - encrypts a message by PROCESS original data / message. In simple words, it runs printing it in reverse order. the encryption algorithm in reverse sequence. Procedure Cryptosystems that use the same key to Conversion encrypt and decrypt messages. Algorithm == Techniques Block cipher - operates on blocks of a fixed Cryptology - defined as the study of size, usually 64 or 128 bits. cryptography or cryptanalysis. Stream Ciphers - generate a stream of Cryptology and cryptanalysis - are the pseudo-random bits, usually either one bit or disciplines that relate to cryptography and byte at a time. techniques like microdots and image-word Confusion - refers to methods used to hide merging help hide information in transit or relationships between the plaintext, the storage. ciphertext, and the key.  1. In-transit encryption - protects data sent Lecture 4 - ENCRYPTING & DECRYPTING Lecture 3 – Brute Force Technique from one machine to another: data is encrypted WITH THE TRANSPOSITION CIPHER before being sent and decrypted after being Attack Models - a set of assumptions about received, as in encrypted connections to Transposition Ciphers how attackers might interact with a cipher and ecommerce websites. what they can and can’t do. 2. At-rest encryption - protects data stored on Transposition cipher technique - the plaintext Black-box Model - access rights based on who an information system. Data is encrypted remains the same, there is no text replacement wrote the code, what the code is trying to do, before being written to memory and decrypted of alphabets or numbers occurs but the order of where it was installed from, and who is trying to before being read. characters are changes or reorder to produce turn it. 3.Encryption in use - protects your data in to cipher. Gray-box Model - the attacker has access to a memory from compromise or data exfiltration by Columnar Transposition - form of cipher’s implementation. encrypting data while being processed. For transposition cipher in which plain text White Box Model - Attacks with full privilege more information. represent in matrix form. have complete access to the implementation == algorithms. Categories of Breaking an Algorithm == (Lars Knudsen) Different Black-box attack models 1.Ciphertext-only attackers (COA) - observe 1.Total Break - A cryptanalyst finds the key. ciphertexts but don’t know the associated 2.Global deduction - A cryptanalyst finds an plaintexts, and don’t know how the plaintexts alternate algorithm. were selected. 3.Instance (or local) deduction - A 2.Known-plaintext attackers (KPA) - observe cryptanalyst finds the plaintext of an intercepted ciphertext and plaintext and do know the ciphertext. associated secret key. 4.Information deduction - A cryptanalyst gains 3.Chosen-plaintext attackers (CPA) - can some information about the key or plaintext. perform encryption queries for plaintexts of their == choice and observe the resulting ciphertexts. Unconditional Security == Cryptographic system - considered to be Models of Gray-Box Models unconditionally secure, sometimes called 1.Side-channel attacks - a source of strong, if it cannot be broken, even with infinite information that depends on the implementation computational resources. of the cipher, be it in software or hardware. Brute Force - means the illegal effort of 2.Invasive attacks - a family of attacks on breaking into the back end of a system to get cipher implementations that are more powerful the username/password combination. than side-channel attacks, and more expensive Brute-force attack - The technique of trying because they require sophisticated equipment. every possible decryption key. == 3 Types of Encryption Applications (Security)