Which statements are correct

$$ Electronic code book mode $($ECB$)$ allows for a simple block cipher encryption of large input plaintext by breaking the plaintext into subsequent blocks.

$$ Insecure communication channels may include Internet, GSM$,$ wireless networks $($Wi$-$Fi$).$

$$ Letter frequency analysis attack is considered effective against substitution cipher because identical plaintexts map to identical ciphertexts.

$$ Double encryption using DES may seem secure but is prone to the meet$-$in$-$the$-$middle attack.

$4.$ Which of the statements below are correct

$$ A condition for the affinity cipher to work with a key $($a$,$b$)$ is that for having a greatest common divisor for a and m $($number of letters in alphabet$)$ equal to $1,$ which will mean that the cipher's encryption function is injective.

$$ In cryptography unencrypted message is referred to as the plaintext, while the encrypted message is referred to as the ciphertext.

$$ An exhaustive key search attack $($brute$-$force type of attack$)$ is considered effective against substitution cipher.

$$ Unconditional security of a cipher can be referred to as information$-$theoretic security $($meaning it cannot be broken even with infinite computing resources$)$ and is only true for the OTP cipher, however under a condition that the truly random key $($of length such as of the plaintext message$)$ can be distributed between the parties, which can only be done unconditionally securely using the quantum key distribution.

$5.$ Which of these statements are correct

$$ Cryptography can be generally divided into symmetric $($public$-$key$)$ and asymmetric $($private$-$key$)$ cryptography.

$$ A linear feedback shift register $($LSFR$)$ has an input bit being a linear function of its previous state and can be easily implemented from flip$-$flops, however due to security issues it was not used in any practical cryptographic scenario.

$$ Permutation is an example of diffusion in a block cipher.

$$ Stream ciphers encrypt individual bits using public keys.