The '256' in AES-256-CBC represents the key size used for encryption, which is 256 bits. This means that the encryption algorithm uses a key that is 256 bits long, providing a high level of security.
In general, larger key sizes increase the difficulty of brute-force attacks, making it harder for unauthorized users to decrypt the data without the correct key. AES supports key sizes of 128, 192, and 256 bits, with 256 bits being the most secure option.
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