BOLT 3: fix definition of flip(B) in P. #779
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rustyrussell
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Interesting, I hadn't visited that part of our code much to be honest. |
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The spec says everything should be big-endian, even our bitfields (thought that is, of course, insane). Here we treat the sha as a little-endian bitfield, which is natural and wholesome, but not in line with the rest of the BOLTs. |
t-bast
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Jul 2, 2020
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ysangkok
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Jul 6, 2020
03-transactions.md
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| Where "flip(B)" alternates the B'th least significant bit in the value P. | ||
| Where "flip(B)" alternates the (B mod 8)'th bit of the (B div 8)'th | ||
| byte of the value. So, "flip(0) in e3b0..." is "e2b0...", and | ||
| "flip(10) in "e3b0..." is "e3b4". |
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why does the last hex string have no "..."?
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Thanks, fixed!
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It turns out everyone does `P[B / 8] ^= (1 << (P % 8))`, which is not what the spec says to do (it implies you would treat P as a bitstring numbered 255 to 0). See this stackoverflow question: https://stackoverflow.com/questions/49928131/lightning-secret-generation-from-seed Reported-by: Janus Troelsen @ysangkok (on Twitter) Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
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t-bast
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OK, I felt it a little dangerous to add "th" to the word list, so I removed the "'th" instead. |
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It turns out everyone does
P[B / 8] ^= (1 << (P % 8)), which is not what the spec says to do (it implies you would treat P as a bitstring numbered 255 to 0).See this stackoverflow question:
https://stackoverflow.com/questions/49928131/lightning-secret-generation-from-seed
Reported-by: Janus Troelsen @ysangkok (on Twitter)
Signed-off-by: Rusty Russell rusty@rustcorp.com.au