What is the maximum allowable key size of the Rijndael encryption algorithm?

The correct answer is C. 256 bits. The Rijndael encryption algorithm supports three key sizes: 128, 192, and 256 bits. The maximum allowable key size is 256 bits. When NIST standardized Rijndael as AES (Advanced Encryption Standard), it adopted all three key sizes (AES-128, AES-192, AES-256) while fixing the…

Submitted by jakub_pl· Apr 18, 2026Cryptography

Question

Options

A128 bits
B192 bits
C256 bits
D512 bits

How the community answered

(53 responses)

A
2% (1)
B
2% (1)
C
91% (48)
D
6% (3)

Explanation

The Rijndael encryption algorithm supports three key sizes: 128, 192, and 256 bits. The maximum allowable key size is 256 bits. When NIST standardized Rijndael as AES (Advanced Encryption Standard), it adopted all three key sizes (AES-128, AES-192, AES-256) while fixing the block size at 128 bits. A 512-bit key is not part of the Rijndael specification.

Topics

#Rijndael#AES#Key size#Symmetric encryption

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