C839 - INTRODUCTION TO CRYPTOGRAPHY QUESTIONS WITH COMPLETE SOLUTIONS

Block Size: 128 bits Key Size: 128, 192, or 256 bits Rounds: 32 Network: Substitution-Permutation Tiny Encryption Algorithm (TEA) CORRECT ANSWERS: Symmetric Block Cipher Block Size: 64 bits Key Size: 128 bits Cryptography CORRECT ANSWERS: Deciphering secret writings, kryptos means hidden and grafo means write. Must not be readable by interlopers over secure/hidden communications. Readable by intended recipients only. Mono-Alphabet Substitution Algorithms CORRECT ANSWERS: Include Ceasar, Atbash, Affine and ROT13 Caeser Cipher CORRECT ANSWERS: Is one of the oldest methods, was used by ancient Romans. Shift of letter. Easy to crack to common words like "A" and "The". Single Substitution Weakness CORRECT ANSWERS: Using common words (A, THE, OO, EE) in English Lang to brute force single substitution ciphers. Null Cipher CORRECT ANSWERS: Hidden message in unrelated text • The sender and recipient have prearranged to use some pattern, taking certain letters from the message. Book Cipher CORRECT ANSWERS: Parties agree on a particular book. Simplest implementation to send coordinates for words Rail Fence Cipher CORRECT ANSWERS: Widely known Transposition cipher. Plaintext written in columns and transposed in rows. Recipient reconstructs the original message Symmetric Key Cryptography uses two processes CORRECT ANSWERS: Substitution (XOR the PT with key) and transposition (swapping blocks of text) DES (Data Encryption Standard) CORRECT ANSWERS: Symmetric Block Cipher Block Size: 64 bit Key Size: 56 bit Rounds: 16 rounds