1. Block Ciphers (like AES) vs. Asymmetric Ciphers (like RSA)

AES (Advanced Encryption Standard) is a symmetric or secret-key encryption algorithm.

It uses the same key for both encryption and decryption. It operates on blocks of data (typically 128 bits or 16 bytes). The Cipher class can easily handle varying input sizes because it can Process data in blocks: It divides the input into blocks, encrypts each block, and then concatenates them. Use padding techniques: To ensure each block is the correct size, padding schemes like PKCS#5/PKCS#7 are used to add extra bytes to the last block. RSA (Rivest-Shamir-Adleman) is an asymmetric or public-key encryption algorithm.

It uses a pair of keys: a public key for encryption and a private key for decryption. It has limitations on the size of data it can directly encrypt. This is due to the mathematical operations involved in RSA encryption, which become computationally expensive with larger inputs.

2. Cipher Class Behavior

AES: OutputSize: Returns the correct output size (multiple of 16 bytes) because AES encryption typically produces an output of the same size as the input (after padding). BlockSize: Returns the correct block size (16 bytes). Automatic Encryption: The Cipher class can often handle the block-by-block encryption process internally for AES, providing a more convenient interface. RSA: OutputSize: Might return an incorrect or misleading value. RSA encryption often has strict limitations on the size of data that can be directly encrypted. BlockSize: Often returns 0 because RSA encryption doesn't operate in fixed-size blocks in the same way as a block cipher like AES. Manual Encryption: You typically need to: Divide the input data into smaller chunks. Encrypt each chunk individually using the RSA public key. Combine the encrypted chunks (e.g., by concatenating them).

3. Key Considerations

AES Key Size: AES can use various key sizes (e.g., 128, 192, 256 bits). RSA Key Size: Common RSA key sizes include 1024, 2048, and 4096 bits. The larger the key size, the stronger the encryption, but also the slower the performance.