Break early on composites in the primality test.

|a| is usually much smaller than |w_bits|. We only need to loop up to
|w_bits| and hide |a| when the value is possibly composite. If
Miller-Rabin has not hit -1 by then, break early.

This speeds up RSA keygen by a bit.

Did 248 RSA 2048 key-gen operations in 30041496us (8.3 ops/sec)
  min: 31690us, median: 109097us, max: 373911us
Did 71 RSA 3072 key-gen operations in 30096719us (2.4 ops/sec)
  min: 108650us, median: 370844us, max: 1768070us
Did 27 RSA 4096 key-gen operations in 32829007us (0.8 ops/sec)
  min: 205485us, median: 1107051us, max: 4035040us

Did 340 RSA 2048 key-gen operations in 30026342us (11.3 ops/sec)
  min: 24681us, median: 77749us, max: 350477us
Did 67 RSA 3072 key-gen operations in 30089075us (2.2 ops/sec)
  min: 75070us, median: 394220us, max: 1101562us
Did 38 RSA 4096 key-gen operations in 30283788us (1.3 ops/sec)
  min: 284947us, median: 742688us, max: 1970468us

Change-Id: If1b48e9306c3fe1be56c304143e206c3bdb3301d
Commit-Queue: David Benjamin <>
Reviewed-by: Adam Langley <>
1 file changed
tree: 91b7ddb3c2cb5da5b2edddc71e92fc3b4da66569
  1. .clang-format
  2. .github/
  3. .gitignore
  7. CMakeLists.txt
  15. codereview.settings
  16. crypto/
  17. decrepit/
  18. fuzz/
  19. go.mod
  20. include/
  21. sources.cmake
  22. ssl/
  23. third_party/
  24. tool/
  25. util/


BoringSSL is a fork of OpenSSL that is designed to meet Google's needs.

Although BoringSSL is an open source project, it is not intended for general use, as OpenSSL is. We don't recommend that third parties depend upon it. Doing so is likely to be frustrating because there are no guarantees of API or ABI stability.

Programs ship their own copies of BoringSSL when they use it and we update everything as needed when deciding to make API changes. This allows us to mostly avoid compromises in the name of compatibility. It works for us, but it may not work for you.

BoringSSL arose because Google used OpenSSL for many years in various ways and, over time, built up a large number of patches that were maintained while tracking upstream OpenSSL. As Google's product portfolio became more complex, more copies of OpenSSL sprung up and the effort involved in maintaining all these patches in multiple places was growing steadily.

Currently BoringSSL is the SSL library in Chrome/Chromium, Android (but it's not part of the NDK) and a number of other apps/programs.

Project links:

There are other files in this directory which might be helpful: