Cryptohack

The Solution is shared considering CAN I SHARE MY SOLUTIONS? Problem AES, like all good block ciphers, performs a “keyed permutation”. This means that it maps every possible input block to a unique output block, with a key determining which permutation to perform. A “block” just refers to a fixed number of bits or bytes, which may represent any kind of data. AES processes a block and outputs another block. We’ll be specifically talking the variant of AES which works on 128 bit (16 byte) blocks and a 128 bit key, known as AES-128. ...

The Solution is shared considering CAN I SHARE MY SOLUTIONS? Problem If a block cipher is secure, there should be no way for an attacker to distinguish the output of AES from a random permutation of bits. Furthermore, there should be no better way to undo the permutation than simply bruteforcing every possible key. That’s why academics consider a cipher theoretically “broken” if they can find an attack that takes fewer steps to perform than bruteforcing the key, even if that attack is practically infeasible. ...

The Solution is shared considering CAN I SHARE MY SOLUTIONS? Problem All operations in RSA involve modular exponentiation. Modular exponentiation is an operation that is used extensively in cryptography and is normally written like: 210 mod 17 You can think of this as raising some number to a certain power (210 = 1024), and then taking the remainder of the division by some other number (1024 mod 17 = 4). In Python there’s a built-in operator for performing this operation: pow(base, exponent, modulus) ...

The Solution is shared considering CAN I SHARE MY SOLUTIONS? Problem Another common encoding scheme is Base64, which allows us to represent binary data as an ASCII string using 64 characters. One character of a Base64 string encodes 6 bits, and so 4 characters of Base64 encode three 8-bit bytes. Base64 is most commonly used online, so binary data such as images can be easily included into HTML or CSS files. ...

The Solution is shared considering CAN I SHARE MY SOLUTIONS? Problem Cryptosystems like RSA works on numbers, but messages are made up of characters. How should we convert our messages into numbers so that mathematical operations can be applied? The most common way is to take the ordinal bytes of the message, convert them into hexadecimal, and concatenate. This can be interpreted as a base-16 number, and also represented in base-10. ...