Prose editing #375
Prose editing #375
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rows 1-111
src/block-ciphers.rst
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| A block cipher is a *keyed permutation*. First, the key determines exactly which | ||
| blocks are mapped. Second, the permutation aspect allows mapping of all possible blocks | ||
| to other blocks. Permutation is important because the recipient must map blocks back to the | ||
| original blocks by analyzing one-to-one. |
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Not entirely sure about this paragraph.
First, the key determines exactly which blocks are mapped.
That's true, but I'm worried that it implies that not all blocks are mapped under all keys, but that's not true. It changes which blocks map to which blocks, but all blocks are always mapped to something.
Second, the permutation aspect allows mapping of all possible blocks to other blocks. Permutation is important because the recipient must map blocks back to the original blocks by analyzing one-to-one.
I don't really understand "by analyzing one-to-one.", maybe without it'd be fine? Or "must be able to map blocks back..."?
src/block-ciphers.rst
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| computes the inverse permutation. In :numref:`fig-BlockCipherDecryption`, | ||
| you can see that we get the same illustration, except that all the arrows are | ||
| going in the other direction. | ||
| we get the same illustration. The exception is that all arrowheads point |
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This seems to imply that it's only accidentally the case that the arrowheads are reversed, but that's a fundamental property. Perhaps "The difference is" or "The difference between the illustrations is"?
src/block-ciphers.rst
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| The only way to know which block maps to which other block, is to know | ||
| the key. A different key will lead to a completely different set of | ||
| Knowing the key helps in understanding which block maps to other blocks. |
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It's important that the key defines which blocks map to which; perhaps "helps in understanding" implies that you know e.g. 10% of them normally but you need the key to know all of them, whereas in reality you need the key to know any of them. Consider "The key defines which blocks map to which blocks". (It's also maybe not entirely accurate to say "which blocks map to which other blocks" since you'll typically have a few blocks that map to themselves under any key. They're rare, but it happens.)
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Looks great! |
rows 1-111