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nip45: negate pow attacks on hyperloglog using a stupid hack.

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fiatjaf 2024-11-03 16:49:02 -03:00
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@ -41,13 +41,14 @@ This is so it enables merging results from multiple relays and yielding a reason
### Algorithm ### Algorithm
The HLL value must be calculated with a precision of `8`, i.e. with 256 registers. This section describes the steps a relay should take in order to return HLL values to clients.
To compute HLL values, first initi the 256 registers to `0` each; then, for on every event to be counted, 1. Upon receiving a filter, if it has a single `#e`, `#p`, `#a` or `#q` item, read its 32th ascii character as a byte and take its modulo over 24 to obtain an `offset` -- in the unlikely case that the filter doesn't meet these conditions, set `offset` to the number 16;
2. Initialize 256 registers to 0 for the HLL value;
1. take byte `16` of the `id` and use it to determine the register index; 3. For all the events that are to be counted according to the filter, do this:
2. count the number of leading zero bits in the following bytes `17..24` of the `id`; 1. Read byte at position `offset` of the event `pubkey`, its value will be the register index `ri`;
3. if the number of leading zeros is bigger than what was previously stored in that register, overwrite it. 2. Count the number of leading zero bits starting at position `offset+1` of the event `pubkey`;
3. Compare that with the value stored at register `ri`, if the new number is bigger, store it.
That is all that has to be done on the relay side, and therefore the only part needed for interoperability. That is all that has to be done on the relay side, and therefore the only part needed for interoperability.