![]() ![]() The block cipher function takes a certain amount of data at a time and consider it as a single block and then encrypt it with a key. Thus the computation of this function is deterministic and easy. It’s a reversible function as Dec(k,(Enc(K,m)) = m, where Dec=decryption function, Enc=Encryption function, k=private key, K=public key is generates and used with the key produce the corresponding ciphertext.īlock Cipher Function: n bits ⟶ 2^n possible block options Message(i)+(key + pseudorandom bitstream generation)⟶ciphertext(i), for each bit of plaintext message, a different random no. Stream cipher processes in a single bit/byte at a time Many use Product Ciphers which is a combination of substitution ciphers and transposition ciphers in succession to improve the security of their network.īlock cipher processes in blocks(multiple bits at a time) There could be many transposition ciphers depending upon the orientation of plaintexts like we could use a tree of plaintext and then write the ciphertext in a definite pattern or you could create a ciphertext by using alternate texts of plaintext, there could be many ways like these. The adversary or attacker could use a known-plaintext against the ciphertext and hence decipher it all. These ciphers are vulnerable to cryptanalysis as the alphabet’s values do not change and the frequency distribution is the same. We start backward with the key and read it as, so starting with column no. So our key is, hence the ciphertext will be as: With the key length of n, there would be n! keys T E R x (x here is padded alphabet as there was a void) We have n=4 i.e., key( k) is of length 4, k=Īnd we all know that the key length specifies the number of columns. It determines the column order and is a permutation of a set of size n(Key length(n) corresponds to n columns). The key to this type of encryption is very unique though. In this type of cipher, the plaintexts alphabets are listed row by row and the ciphertext alphabets are retrieved column by column. These ciphers are created by re-arranging the order/positions of the alphabets without altering their values. So, let’s take it further to other types. Continuing our discussion on Symmetric Cryptography, we have previously discussed the different types of ciphers in Symmetric Cryptography. ![]()
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