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@ nostr_cn_dev
2025-04-15 01:26:59NIP-13
Proof of Work
draftoptionalThis NIP defines a way to generate and interpret Proof of Work for nostr notes. Proof of Work (PoW) is a way to add a proof of computational work to a note. This is a bearer proof that all relays and clients can universally validate with a small amount of code. This proof can be used as a means of spam deterrence.
difficultyis defined to be the number of leading zero bits in theNIP-01id. For example, an id of000000000e9d97a1ab09fc381030b346cdd7a142ad57e6df0b46dc9bef6c7e2dhas a difficulty of36with36leading 0 bits.002f...is0000 0000 0010 1111...in binary, which has 10 leading zeroes. Do not forget to count leading zeroes for hex digits <=7.Mining
To generate PoW for a
NIP-01note, anoncetag is used:json {"content": "It's just me mining my own business", "tags": [["nonce", "1", "21"]]}When mining, the second entry to the nonce tag is updated, and then the id is recalculated (see NIP-01). If the id has the desired number of leading zero bits, the note has been mined. It is recommended to update the
created_atas well during this process.The third entry to the nonce tag
SHOULDcontain the target difficulty. This allows clients to protect against situations where bulk spammers targeting a lower difficulty get lucky and match a higher difficulty. For example, if you require 40 bits to reply to your thread and see a committed target of 30, you can safely reject it even if the note has 40 bits difficulty. Without a committed target difficulty you could not reject it. Committing to a target difficulty is something all honest miners should be ok with, and clientsMAYreject a note matching a target difficulty if it is missing a difficulty commitment.Example mined note
json { "id": "000006d8c378af1779d2feebc7603a125d99eca0ccf1085959b307f64e5dd358", "pubkey": "a48380f4cfcc1ad5378294fcac36439770f9c878dd880ffa94bb74ea54a6f243", "created_at": 1651794653, "kind": 1, "tags": [ ["nonce", "776797", "20"] ], "content": "It's just me mining my own business", "sig": "284622fc0a3f4f1303455d5175f7ba962a3300d136085b9566801bc2e0699de0c7e31e44c81fb40ad9049173742e904713c3594a1da0fc5d2382a25c11aba977" }Validating
Here is some reference C code for calculating the difficulty (aka number of leading zero bits) in a nostr event id:
```c int zero_bits(unsigned char b) { int n = 0;
if (b == 0) return 8; while (b >>= 1) n++; return 7-n;}
/ find the number of leading zero bits in a hash / int count_leading_zero_bits(unsigned char *hash) { int bits, total, i; for (i = 0, total = 0; i < 32; i++) { bits = zero_bits(hash[i]); total += bits; if (bits != 8) break; } return total; } ```
Here is some JavaScript code for doing the same thing:
```javascript // hex should be a hexadecimal string (with no 0x prefix) function countLeadingZeroes(hex) { let count = 0;
for (let i = 0; i < hex.length; i++) { const nibble = parseInt(hex[i], 16); if (nibble === 0) { count += 4; } else { count += Math.clz32(nibble) - 28; break; } }
return count; } ```
Delegated Proof of Work
Since the
NIP-01note id does not commit to any signature, PoW can be outsourced to PoW providers, perhaps for a fee. This provides a way for clients to get their messages out to PoW-restricted relays without having to do any work themselves, which is useful for energy-constrained devices like mobile phones.