\( a=5 \) and \( b=39 \) with a simple table. You can easily compute \( \gcd(a, b) \), \( \lambda \) and \( \mu \) for e.g. if Alice wants to send the message "Hey Bob!" encrypted to Bob with a symmetric key cryptosystem, she first converts it into its integer representation and then into its binary representation: we have prepended an extra 0): CharacterĮ.g. A part of the ASCII table from Wikipedia is listed in the following table (notice that the binary representation on the Wikipedia site is only seven bits but we use eight bits, i.e. Therefore, we have to convert the characters into integers or bits before we apply the cryptosystem to the message.īecause a computer can only handle bits, there already exists a method for converting characters into integers or bits, that uses the ASCII (American Standard Code for Information Interchange) table. And symmetric key cryptosystems (Alice and Bob uses the same key) such as DES and AES are based on bitwise operations on bits (a bit is either equal 0 or 1 and is an abbreviation for binary digit). That is, the substitution is fixed for each letter of the alphabet. In cryptography we often encrypt and sign messages that contains characters, but asymmetric key cryptosystems (Alice and Bob uses different keys) such as RSA and ElGamal are based on arithmetic operations on integer. A monoalphabetic substitution cipher, also known as a simple substitution cipher, relies on a fixed replacement structure.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |