goals attacks attack types terms in information security cipher cipher cipher inverse cipher encryption cipher decryption cipher cipher 13. Vernam cipher 14. Vigenere cipher cipher 16. Railfence cipher when depth not given cipher of alphabets algorithm Euclidean algorithm 's Totient function 's Theorem 's Theorem 24 .Chinese Remainder Theorem 25)Diffie Hellman Key Exchange Cryptosystem 26) Simplified DES(Data Encryption standard) 27)RSA algorithm 28) Elgamal Digital Signature Scheme