The test vectors listed in
Are represented as Hex strings? I'm sure that the key is, because it's length is 32. And each hex digit, nibble, is 4 bits. So 32x4=128. But what about the stream generated? How are they represented?
1 Answer
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Yes. The stream is also in hexadecimal, as is the IV if used.
The representation is just the output stream broken into 64-byte sections. Some of the tests output 512 bytes of stream, some output 131072.
answered Nov 14, 2015 at 20:49
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$\begingroup$ Thanks Richie. But There has to be some difference. The length of the Key is 32 hex (wich is 128 bits). But the length of the stream is 512 (32 x 16). But in the beginning it says "stream is generated by encrypting 512 zero bytes". I believed that the stream is generated first and every bit of that stream is XORed with the 512 zero message". It should say bits, not bytes, right? $\endgroup$– MarkNov 14, 2015 at 22:54
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$\begingroup$ The Key is 32 (hex) x4 = 128 bits (because each hex represents 4 bits, a nibble). Applying the same logic to the generated key stream 32 (hex) x 16 (rows) = 512 hex x 4 = 2048 bits. $\endgroup$– MarkNov 15, 2015 at 0:22
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$\begingroup$ @Mark Yes, but the key stream is broken up in blocks because the blocks are not successive. Take a good look at the start / end of the blocks. You are right about the key of course. $\endgroup$– Maarten Bodewes ♦Nov 15, 2015 at 0:26
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$\begingroup$ You're right Maarten! The blocks are not succesive. For example, the first block is stream[0..63] which cardinal is 64. The result is a 128 hex x 4 = 512 bits (per block). As the block has 64 elements, 512/64 = 8. Hence, each element of the block is a byte. Am I correct now? Thanks $\endgroup$– MarkNov 15, 2015 at 1:01
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$\begingroup$ @Mark each 2-octet element of the block is a byte, yes. $\endgroup$ Nov 16, 2015 at 6:20