├── .circleci └── config.yml ├── .gitignore ├── LICENSE ├── README.md ├── pom.xml ├── spotbugs.xml └── src ├── main └── java │ └── com │ └── codahale │ └── fastuuid │ └── UUIDGenerator.java └── test └── java └── com └── codahale └── fastuuid ├── Benchmarks.java └── tests └── UUIDGeneratorTest.java /.circleci/config.yml: -------------------------------------------------------------------------------- 1 | # 2 | # Copyright © 2017 Coda Hale (coda.hale@gmail.com) 3 | # 4 | # Licensed under the Apache License, Version 2.0 (the "License"); 5 | # you may not use this file except in compliance with the License. 6 | # You may obtain a copy of the License at 7 | # 8 | # http://www.apache.org/licenses/LICENSE-2.0 9 | # 10 | # Unless required by applicable law or agreed to in writing, software 11 | # distributed under the License is distributed on an "AS IS" BASIS, 12 | # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 | # See the License for the specific language governing permissions and 14 | # limitations under the License. 15 | # 16 | 17 | version: 2 18 | jobs: 19 | build: 20 | docker: 21 | - image: maven:3-jdk-12-alpine 22 | working_directory: ~/repo 23 | environment: 24 | MAVEN_OPTS: -Xmx3200m 25 | steps: 26 | - checkout 27 | - restore_cache: 28 | keys: 29 | - v1-dependencies-{{ checksum ".circleci/config.yml" }}-{{ checksum "pom.xml" }} 30 | # fallback to using the latest cache if no exact match is found 31 | - v1-dependencies- 32 | - run: mvn clean verify 33 | - save_cache: 34 | paths: 35 | - ~/.m2 36 | key: v1-dependencies-{{ checksum ".circleci/config.yml" }}-{{ checksum "pom.xml" }} 37 | - run: 38 | name: Save test results 39 | command: | 40 | mkdir -p ~/junit/ 41 | find . -type f -regex ".*/target/surefire-reports/.*xml" -exec cp {} ~/junit/ \; 42 | when: always 43 | - store_test_results: 44 | path: ~/junit 45 | - store_artifacts: 46 | path: ~/junit 47 | -------------------------------------------------------------------------------- /.gitignore: -------------------------------------------------------------------------------- 1 | target/ 2 | pom.xml.tag 3 | pom.xml.releaseBackup 4 | pom.xml.versionsBackup 5 | pom.xml.next 6 | release.properties 7 | dependency-reduced-pom.xml 8 | buildNumber.properties 9 | .mvn/timing.properties 10 | -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | 2 | Apache License 3 | Version 2.0, January 2004 4 | http://www.apache.org/licenses/ 5 | 6 | TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 7 | 8 | 1. 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We also recommend that a 186 | file or class name and description of purpose be included on the 187 | same "printed page" as the copyright notice for easier 188 | identification within third-party archives. 189 | 190 | Copyright [yyyy] [name of copyright owner] 191 | 192 | Licensed under the Apache License, Version 2.0 (the "License"); 193 | you may not use this file except in compliance with the License. 194 | You may obtain a copy of the License at 195 | 196 | http://www.apache.org/licenses/LICENSE-2.0 197 | 198 | Unless required by applicable law or agreed to in writing, software 199 | distributed under the License is distributed on an "AS IS" BASIS, 200 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 201 | See the License for the specific language governing permissions and 202 | limitations under the License. 203 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # fast-uuid 2 | 3 | [![CircleCI](https://circleci.com/gh/codahale/fast-uuid.svg?style=svg)](https://circleci.com/gh/codahale/fast-uuid) 4 | 5 | **N.B.: This is a cool design, but is only an order of magnitude faster than the Java 12 standard library. Just use that instead.** 6 | 7 | I dunno, man. It generates v4 UUIDs really quickly. 8 | 9 | ## How quickly 10 | 11 | ``` 12 | Benchmark Mode Cnt Score Error Units 13 | Benchmarks.fast avgt 25 48.554 ± 0.568 ns/op 14 | Benchmarks.stdLib avgt 25 1440.938 ± 30.051 ns/op 15 | ``` 16 | 17 | ## Ok but how tho 18 | 19 | Instead of `SecureRandom`, `UUIDGenerator` uses 20 | [SipHash-2-4](https://131002.net/siphash/siphash.pdf) in a 21 | [fast-key-erasure](https://blog.cr.yp.to/20170723-random.html) CSPRNG. 22 | 23 | For each UUID, it uses SipHash-2-4 to hash four single-byte values selected for their high Hamming 24 | distances from each other. The first two results are used to re-key the hash; the second two are 25 | used to produce the UUID. 26 | 27 | For UUIDs, a few key properties are desirable: 28 | 29 | 1. They should be uniformly distributed to reduce the probability of collisions. 30 | 2. Anyone who collects a set of UUIDs should be unable to determine which UUIDs were generated and 31 | which UUIDs will be generated. 32 | 3. Anyone who gets privileged access to the computer generating UUIDs should be unable to determine 33 | which UUIDs were previously generated. 34 | 35 | This library attempts to provide those properties. 36 | 37 | **N.B.: I'm not a cryptographer, so no cryptographer evaluated this design. Do not use this without 38 | hiring a cryptographer to evaluate it.** 39 | 40 | For the first property, SipHash is a cryptographically strong PRF, which should make it 41 | indistinguishable from a uniform random function. The UUIDs generated from its output, therefore, 42 | should also be uniformly distributed. 43 | 44 | For the second property, consider the information an attacker might collect: `{h(k, C), h(k, D)}`. 45 | In order to calculate future values, an attacker would need to learn information about `k`. SipHash 46 | is a strong MAC, however, which means key recovery attacks should be as difficult as brute force. 47 | Without the ability to recover `k`, the attacker would find it doubly difficult to calculate past 48 | values (e.g. `h(k, C)` given `h(h(k, A) . h(k, B), C)`). 49 | 50 | For the third property, consider the information an attacker might collect: `h(h(k, A) . h(k, B), 51 | A)`. Again, because SipHash is a strong MAC, an attacker should be unable to recover information 52 | about `k` and therefore unable to calculate past values (e.g. `h(k, C)`). Of course, they *will* be 53 | able to calculate future values, so don't let attackers look at your memory. 54 | 55 | ## Fascinating 56 | 57 | What can I say. I got bored. 58 | 59 | ## License 60 | 61 | Copyright © 2018 Coda Hale 62 | 63 | Distributed under the Apache License 2.0. 64 | -------------------------------------------------------------------------------- /pom.xml: -------------------------------------------------------------------------------- 1 | 2 | 19 | 22 | 4.0.0 23 | 24 | 25 | com.codahale 26 | common-pom 27 | 0.0.19 28 | 29 | 30 | fast-uuid 31 | 0.1.0-SNAPSHOT 32 | fast-uuid 33 | https://github.com/codahale/fast-uuid 34 | 35 | A high-performance UUIDv4 generator. 36 | 37 | 38 | 2018 39 | 40 | 41 | scm:git:https://github.com/codahale/fast-uuid.git 42 | scm:git:https://github.com/codahale/fast-uuid.git 43 | https://github.com/codahale/fast-uuid 44 | HEAD 45 | 46 | 47 | 48 | 49 | 50 | 51 | org.apache.maven.plugins 52 | maven-jar-plugin 53 | 54 | 55 | 56 | com.codahale.fastuuid 57 | 58 | 59 | 60 | 61 | 62 | 63 | 64 | 65 | -------------------------------------------------------------------------------- /spotbugs.xml: -------------------------------------------------------------------------------- 1 | 18 | 19 | -------------------------------------------------------------------------------- /src/main/java/com/codahale/fastuuid/UUIDGenerator.java: -------------------------------------------------------------------------------- 1 | /* 2 | * Copyright © 2018 Coda Hale (coda.hale@gmail.com) 3 | * 4 | * Licensed under the Apache License, Version 2.0 (the "License"); 5 | * you may not use this file except in compliance with the License. 6 | * You may obtain a copy of the License at 7 | * 8 | * http://www.apache.org/licenses/LICENSE-2.0 9 | * 10 | * Unless required by applicable law or agreed to in writing, software 11 | * distributed under the License is distributed on an "AS IS" BASIS, 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 | * See the License for the specific language governing permissions and 14 | * limitations under the License. 15 | */ 16 | package com.codahale.fastuuid; 17 | 18 | import java.security.SecureRandom; 19 | import java.util.UUID; 20 | 21 | /** 22 | * A class which generates {@link UUID} instances using SipHash-2-4 in a fast-key-erasure CSPRNG. 23 | * 24 | *

For each UUID, it uses SipHash-2-4 to hash four single-byte values selected for their high 25 | * Hamming distances from each other. The first two results are used to re-key the hash; the second 26 | * two are used to produce the UUID. 27 | * 28 | *

This design allows for very fast UUID generation (~50ns/UUID) as well as forward-secrecy (i.e. 29 | * a compromised generator reveals no information about previously-generated UUIDs). 30 | * 31 | *

To provide backward-secrecy (i.e. a compromised generator reveals no information about UUIDs 32 | * which will be generated), the generator should be periodically re-seeded. 33 | */ 34 | public class UUIDGenerator { 35 | // four bytes selected for their relatively high Hamming distances 36 | private static final byte A = 0b00000110; 37 | private static final byte B = 0b01111111; 38 | private static final byte C = (byte) 0b10111000; 39 | private static final byte D = (byte) 0b11000001; 40 | 41 | // underlying PRNG 42 | private final SecureRandom random; 43 | 44 | // SipHash state 45 | private long v0, v1, v2, v3; 46 | 47 | /** 48 | * Creates a new {@link UUIDGenerator} seeded from the given PRNG. 49 | * 50 | * @param random a PRNG to use for a seed 51 | */ 52 | public UUIDGenerator(SecureRandom random) { 53 | this.random = random; 54 | reseed(); 55 | } 56 | 57 | /** Re-seeds the {@link UUIDGenerator}. */ 58 | public void reseed() { 59 | reseed(random.nextLong(), random.nextLong()); 60 | } 61 | 62 | private void reseed(long k0, long k1) { 63 | // SipHash magic constants 64 | this.v0 = k0 ^ 0x736F6D6570736575L; 65 | this.v1 = k1 ^ 0x646F72616E646F6DL; 66 | this.v2 = k0 ^ 0x6C7967656E657261L; 67 | this.v3 = k1 ^ 0x7465646279746573L; 68 | } 69 | 70 | /** 71 | * Generates a random {@link UUID}. 72 | * 73 | * @return a random {@link UUID} 74 | */ 75 | public UUID generate() { 76 | final long k0 = sipHash24(v0, v1, v2, v3, A); 77 | final long k1 = sipHash24(v0, v1, v2, v3, B); 78 | final long msb = (sipHash24(v0, v1, v2, v3, C) & ~0xF000L) | 0x4000L; 79 | final long lsb = ((sipHash24(v0, v1, v2, v3, D) << 2) >>> 2) | 0x8000000000000000L; 80 | reseed(k0, k1); 81 | return new UUID(msb, lsb); 82 | } 83 | 84 | // a very slimmed-down version of SipHash-2-4 which operates on a single byte 85 | @SuppressWarnings("Duplicates") 86 | private static long sipHash24(long v0, long v1, long v2, long v3, byte data) { 87 | final long m = (data & 0xFFL) | 0x100000000000000L; // simplify the masking 88 | 89 | v3 ^= m; 90 | for (int i = 0; i < 2; i++) { // put the 2 in SipHash-2-4 91 | v0 += v1; 92 | v2 += v3; 93 | v1 = Long.rotateLeft(v1, 13); 94 | v3 = Long.rotateLeft(v3, 16); 95 | 96 | v1 ^= v0; 97 | v3 ^= v2; 98 | v0 = Long.rotateLeft(v0, 32); 99 | 100 | v2 += v1; 101 | v0 += v3; 102 | v1 = Long.rotateLeft(v1, 17); 103 | v3 = Long.rotateLeft(v3, 21); 104 | 105 | v1 ^= v2; 106 | v3 ^= v0; 107 | v2 = Long.rotateLeft(v2, 32); 108 | } 109 | v0 ^= m; 110 | 111 | v2 ^= 0xFF; 112 | for (int i = 0; i < 4; i++) { // put the 4 in SipHash-2-4 113 | v0 += v1; 114 | v2 += v3; 115 | v1 = Long.rotateLeft(v1, 13); 116 | v3 = Long.rotateLeft(v3, 16); 117 | 118 | v1 ^= v0; 119 | v3 ^= v2; 120 | v0 = Long.rotateLeft(v0, 32); 121 | 122 | v2 += v1; 123 | v0 += v3; 124 | v1 = Long.rotateLeft(v1, 17); 125 | v3 = Long.rotateLeft(v3, 21); 126 | 127 | v1 ^= v2; 128 | v3 ^= v0; 129 | v2 = Long.rotateLeft(v2, 32); 130 | } 131 | return v0 ^ v1 ^ v2 ^ v3; 132 | } 133 | } 134 | -------------------------------------------------------------------------------- /src/test/java/com/codahale/fastuuid/Benchmarks.java: -------------------------------------------------------------------------------- 1 | /* 2 | * Copyright © 2018 Coda Hale (coda.hale@gmail.com) 3 | * 4 | * Licensed under the Apache License, Version 2.0 (the "License"); 5 | * you may not use this file except in compliance with the License. 6 | * You may obtain a copy of the License at 7 | * 8 | * http://www.apache.org/licenses/LICENSE-2.0 9 | * 10 | * Unless required by applicable law or agreed to in writing, software 11 | * distributed under the License is distributed on an "AS IS" BASIS, 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 | * See the License for the specific language governing permissions and 14 | * limitations under the License. 15 | */ 16 | package com.codahale.fastuuid; 17 | 18 | import java.security.SecureRandom; 19 | import java.util.UUID; 20 | import java.util.concurrent.TimeUnit; 21 | import org.openjdk.jmh.annotations.Benchmark; 22 | import org.openjdk.jmh.annotations.BenchmarkMode; 23 | import org.openjdk.jmh.annotations.Mode; 24 | import org.openjdk.jmh.annotations.OutputTimeUnit; 25 | import org.openjdk.jmh.annotations.Scope; 26 | import org.openjdk.jmh.annotations.State; 27 | 28 | @BenchmarkMode(Mode.AverageTime) 29 | @OutputTimeUnit(TimeUnit.NANOSECONDS) 30 | @State(Scope.Benchmark) 31 | public class Benchmarks { 32 | private final UUIDGenerator generator = new UUIDGenerator(new SecureRandom()); 33 | 34 | @Benchmark 35 | public UUID fast() { 36 | return generator.generate(); 37 | } 38 | 39 | @Benchmark 40 | public UUID stdLib() { 41 | return UUID.randomUUID(); 42 | } 43 | } 44 | -------------------------------------------------------------------------------- /src/test/java/com/codahale/fastuuid/tests/UUIDGeneratorTest.java: -------------------------------------------------------------------------------- 1 | /* 2 | * Copyright © 2018 Coda Hale (coda.hale@gmail.com) 3 | * 4 | * Licensed under the Apache License, Version 2.0 (the "License"); 5 | * you may not use this file except in compliance with the License. 6 | * You may obtain a copy of the License at 7 | * 8 | * http://www.apache.org/licenses/LICENSE-2.0 9 | * 10 | * Unless required by applicable law or agreed to in writing, software 11 | * distributed under the License is distributed on an "AS IS" BASIS, 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 | * See the License for the specific language governing permissions and 14 | * limitations under the License. 15 | */ 16 | package com.codahale.fastuuid.tests; 17 | 18 | import static org.assertj.core.api.Assertions.assertThat; 19 | import static org.mockito.Mockito.mock; 20 | import static org.mockito.Mockito.when; 21 | 22 | import com.codahale.fastuuid.UUIDGenerator; 23 | import java.security.SecureRandom; 24 | import org.junit.jupiter.api.Test; 25 | 26 | class UUIDGeneratorTest { 27 | @Test 28 | void generating() { 29 | final SecureRandom random = mock(SecureRandom.class); 30 | when(random.nextLong()) 31 | .thenReturn( 32 | 0xb8d59fd5bc12dbb4L, 0x31e9f344b73ee369L, 0xb8d59fd5bc12dbb4L, 0x31e9f344b73ee369L); 33 | 34 | final UUIDGenerator generator = new UUIDGenerator(random); 35 | assertThat(generator.generate().toString()).isEqualTo("88e6891a-3dbc-423c-b51a-127083468307"); 36 | assertThat(generator.generate().toString()).isEqualTo("ad173908-cbe5-49a7-8a36-b516b033b4bd"); 37 | assertThat(generator.generate().version()).isEqualTo(4); 38 | assertThat(generator.generate().variant()).isEqualTo(2); 39 | 40 | generator.reseed(); 41 | assertThat(generator.generate().toString()).isEqualTo("88e6891a-3dbc-423c-b51a-127083468307"); 42 | } 43 | } 44 | --------------------------------------------------------------------------------