Final answer:
The underlying logic of converting plaintext into ciphertext involves encryption techniques such as the transposition cipher.
Step-by-step explanation:
The underlying logic of the process used to convert plaintext into ciphertext is called encryption. Encryption is a technique that transforms data into a secret code to ensure privacy and security. In the context of converting plaintext into ciphertext, there are various encryption algorithms that can be used.
One commonly used encryption algorithm is the transposition cipher, as mentioned in the reference. In a transposition cipher, the letters in the plaintext are rearranged according to a predetermined rule. This rule can involve dividing the plaintext into blocks and making changes to the order of letters within each block. A keyword may be used to determine the block size and the changes made to the order of letters.
For example, if the keyword is 'SECRET' and the plaintext is 'HELLO WORLD', the letters are rearranged based on the order of the keyword. The resulting ciphertext may be 'EOLHW DLROL'. The keyword 'SECRET' determines the block size as 6, and within each block, the order of letters is changed based on the keyword.