Step 1/6
Given the question, it seems there's a misunderstanding or typo in the input block provided for the ByteSub operation in AES. Specifically, "UC" is not a valid hexadecimal value. Hexadecimal values range from 00 to FF, representing values from 0 to 255 in decimal. Each digit in a hexadecimal number represents a value from 0 to 15 (in decimal) or 0 to F (in hexadecimal). Therefore, "UC" cannot be processed in the context of AES or any operation requiring hexadecimal input. Assuming a typo and replacing "UC" with a valid hexadecimal value is necessary to proceed. For the sake of this explanation, let's replace "UC" with "0C" (a common mistake could be misreading or mistyping "0" as "U"). If "UC" was intended to represent something specific or if there's another context, please clarify for an accurate response. Proceeding with "0C" as the correction:
Step 2/6
Identify the input block for the ByteSub operation. Assuming the correction, the input block is EA 04 0C 08 12 45.
Step 3/6
Understand the ByteSub operation. In AES, the ByteSub operation (also known as SubBytes) involves substituting each byte of the input block with a corresponding byte from a predefined S-box. The S-box is a fixed 256-byte (16x16) matrix used for substitution, where each input byte is replaced with the byte at the position determined by its hexadecimal value.
Step 4/6
Given the S-box provided in the question seems to be a simple sequence from 00 to FF, we'll use the input block's hexadecimal values to find the corresponding output values directly. However, the S-box provided in the question is not in a format that allows for direct lookup as it's just a sequence of numbers from 0 to FF without specifying the output values for substitution. In a standard AES S-box, each input byte is replaced with a specific output byte according to the S-box's matrix. Without the actual substitution values, we can't proceed with a real ByteSub operation.
Step 5/6
Assuming a standard AES S-box operation, we would look up each byte of the input block in the S-box and replace it with the corresponding output byte. Since the actual S-box values are not provided, we'll illustrate the process hypothetically:
- For "EA", we would find the row and column in the S-box designated by "E" and "A", respectively, and replace "EA" with the value found at that position.
- Repeat the process for "04", "0C", "08", "12", and "45", finding each in the S-box and replacing it with the corresponding output value.
Answer
Compile the output block by concatenating the substituted values. Without the actual S-box substitution values, we cannot provide a specific output block.
In a real AES ByteSub operation, the S-box is designed to resist linear and differential cryptanalysis by ensuring no fixed points (where input equals output) and no opposite fixed points (where input is the bitwise complement of output) among other properties. The actual output would depend on the specific S-box used, which in the context of AES, is predefined and not a simple sequence.
To accurately answer the question with a specific output block, the actual S-box substitution values or a clarification on the intended process for substitution using the provided sequence is necessary.
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