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85 lines
2.3 KiB
Markdown
85 lines
2.3 KiB
Markdown
NIP-76
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======
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Relay Read Permissions
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----------------------
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`draft` `optional`
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Tag names `rp` (read permission) and `prp` (probabilistic read permission) define which keys are authorized to download an event from the relay.
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Events that include an `rp` or `prp` require AUTH to be downloaded.
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## Read Permission
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The `rp` tag accepts a list of pubkeys
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```json
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["rp", "<pubkey1>", "<pubkey2>", "<pubkey3>"]
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```
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Relays MUST check if the authed user is one of the keys in the `rp` before sending the event to the client.
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## Probabilistic Read Permissions
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Probabilistic permissions use bloom filters that include a set of pubkeys. They are represented by a colon-separated value with:
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1. the size of the bit array
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2. the number of hashing rounds used by the filter
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3. the bit array in Base64.
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```json
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["prp", "<BitArray Size>:<Rounds>:<base64>"]
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```
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Bloom filters MUST use `SHA-256` functions of the key + iterating index as the psedocode below:
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```js
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class BloomFilter(size: Int, rounds: Int, buffer: ByteArray) {
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val bits = BitArray(buffer)
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fun bitIndex(value: ByteArray, index: Byte) {
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return BigInt(sha256(value || index)) % size
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}
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fun add(pubkey: HexKey) {
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val value = pubkey.hexToByteArray()
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for (index in 0 until rounds) {
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bits[bitIndex(value, index)] = true
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}
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}
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fun mightContains(pubkey: HexKey): Boolean {
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val value = pubkey.hexToByteArray()
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for (index in 0 until rounds) {
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if (!bits[bitIndex(value, index)]) {
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return false
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}
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}
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return true
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}
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fun encode() = size + ":" + rounds + ":" + base64Enc(bits.toByteArray()) // base64 might include extra 0 bits to fill the last byte
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fun decode(str: String): BloomFilter {
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val parts = str.split(":")
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return BloomFilter(parts[0].toInt(), parts[1].toInt(), base64Decode(bits.toByteArray()))
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}
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}
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```
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Relays MUST check if the authed user is in the filter before returning the event.
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### Test cases
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The filter below has 100 bits, with 10 rounds or hashes that should be able to match 10,000,000 keys without a single false positive.
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```json
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["prp", "100:10:QGKCgBEBAAhIAApO"]
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```
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It includes keys `ca29c211f1c72d5b6622268ff43d2288ea2b2cb5b9aa196ff9f1704fc914b71b` and `460c25e682fda7832b52d1f22d3d22b3176d972f60dcdc3212ed8c92ef85065c`
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