From 90f4b997dcec1f518563eec58c92b8d77f5e2398 Mon Sep 17 00:00:00 2001 From: Fabian Boemer Date: Tue, 8 Oct 2024 10:51:58 -0700 Subject: [PATCH] Add docs for config size (#119) --- .../ParameterTuning.md | 23 +++++++++++++++---- 1 file changed, 18 insertions(+), 5 deletions(-) diff --git a/Sources/PrivateInformationRetrieval/PrivateInformationRetrieval.docc/ParameterTuning.md b/Sources/PrivateInformationRetrieval/PrivateInformationRetrieval.docc/ParameterTuning.md index 04f8e12e..20585bf7 100644 --- a/Sources/PrivateInformationRetrieval/PrivateInformationRetrieval.docc/ParameterTuning.md +++ b/Sources/PrivateInformationRetrieval/PrivateInformationRetrieval.docc/ParameterTuning.md @@ -18,6 +18,8 @@ PIRProcessDatabase ~/config.json ### Basic Parameters +#### Sharding + Sharding parameters determine the number of shards and the number of entries per shard. Sharding sets a hard upper bound on how much privacy the keyword PIR application has since the server sees the client's desired shard. However, more shards @@ -35,9 +37,19 @@ PIRs automatically. For thin databases, smaller RLWE plaintexts in fits many buckets. Large plaintexts are more efficient for wide databases. -Otherwise, the observed [noise budget](https://swiftpackageindex.com/apple/swift-homomorphic-encryption/main/documentation/homomorphicencryption/ciphertext/noisebudget(using:variabletime:)) is an important parameter to track. If it is low, -then it is best to increase the ciphertext-to-plaintext modulus ratio. -This can be done by either decreasing the plaintext modulus with the same ring dimension +##### Configuration size +Generally, increasing the `shardCount` will yield faster server runtime. +However, since the client needs to know information about each shard, increasing `shardCount` also increases the size of the [PIR configuration](https://swiftpackageindex.com/apple/swift-homomorphic-encryption/main/documentation/privateinformationretrievalprotobuf/apple_swifthomomorphicencryption_api_pir_v1_pirconfig). +One way to reduce the PIR configuration size is to process each shard with the same configuration (see ). +Then, the PIR configuration will be highly compressible, yielding a smaller configuration size when transmitting over a network (that supports compression). + +#### Rlwe Parameters +Different database sizes may have different optimal [RLWE parameters](https://swiftpackageindex.com/apple/swift-homomorphic-encryption/main/documentation/homomorphicencryption/predefinedrlweparameters). +To choose the best RLWE parameters, it is import to track the observed [noise budget](https://swiftpackageindex.com/apple/swift-homomorphic-encryption/main/documentation/homomorphicencryption/ciphertext/noisebudget(using:variabletime:)) is an important parameter to track (e.g. by viewing logs when running [PIRProcessDatabase](https://swiftpackageindex.com/apple/swift-homomorphic-encryption/main/documentation/pirprocessdatabase)) + +If the noise budget is too low, decryption may be incorrect, yielding incorrect PIR lookups. +To increase the noise budge, increase the ciphertext-to-plaintext modulus ratio +by either decreasing the plaintext modulus with the same ring dimension or increasing the ring dimension and ciphertext modulus while keeping the plaintext somewhat similar. For example, if `n_4096_logq_27_28_28_logt_16` exhausts the noise budget, consider trying `n_4096_logq_27_28_28_logt_4`. @@ -64,6 +76,7 @@ and executables. #### Thin Database +We generate a database of 100,000 rows, each with 2 bytes. ```sh PIRGenerateDatabase \ --output-database thinDatabase.txtpb \ @@ -100,12 +113,12 @@ runtime by 50% since each database entry now holds twice as many keyword-value pairs, making the database smaller for keyword PIR. #### Wide Database - +We generate a database of 1000 rows, each with 60,000 bytes. ```json PIRGenerateDatabase \ --output-database wideDatabase.txtpb \ --row-count 1000 \ - --value-size '60000' \ + --value-size 60000 \ --value-type random ```