Final answer:
Cryptographic systems are characterized by the operations used for encryption, the number of keys, and the method of processing plaintext. Attacks on encryption include cryptanalysis, brute-force, and side-channel attacks. A two-way Telegram communication using a symmetric cryptosystem relies on both parties sharing a common key for encryption and decryption.
Step-by-step explanation:
Cryptographic Systems: Dimensions Explained
Cryptographic systems are commonly characterized along three independent dimensions: types of operations used for transforming plaintext to ciphertext, the number of keys used, and the way in which the plaintext is processed. Regarding operations, cryptographic algorithms may use substitution, transposition, or a combination of both. The number of keys used can either be one, for symmetric-key systems, or two, for asymmetric-key systems. The way plaintext is processed could be in blocks (block cipher) or continuously (stream cipher).
Attacks on Conventional Encryption Schemes
Various approaches used in attacking conventional encryption include cryptanalysis, which attempts to deduce the plaintext or key through analysis of the ciphertext; brute-force attacks, which try every possible key until the correct one is found; and side-channel attacks, which exploit physical implementations of the cryptosystem.
Two-Way Telegram Communication Example
In a two-way Telegram communication using the symmetric cryptosystem Model, both the sender and receiver share a common key. When the sender wants to send a message, they use this key to encrypt the plaintext and send the resulting ciphertext. Upon receiving the ciphertext, the receiver uses the same key to decrypt it and obtain the original message. This ensures that the communication is secure from eavesdroppers who do not possess the key.