Improve PBKDF self-tuning

Make the tune interval a build-time configurable instead of hardcoding
it in each source file.

Also use binary search in RFC4880_encode_count instead of linear search.

Fix a bug in Timer

1 files changed, 3 insertions, 3 deletions

diff --git a/src/lib/pbkdf/scrypt/scrypt.cpp b/src/lib/pbkdf/scrypt/scrypt.cpp
index c20225734..e50073669 100644
--- a/src/lib/pbkdf/scrypt/scrypt.cpp
+++ b/src/lib/pbkdf/scrypt/scrypt.cpp
@@ -50,10 +50,10 @@ std::unique_ptr<PasswordHash> Scrypt_Family::tune(size_t output_length,
    size_t r = 1;
    size_t p = 1;
 
-   Timer timer("Scrypt", 0);
-   const std::chrono::milliseconds tune_msec(30);
+   Timer timer("Scrypt");
+   const auto tune_time = BOTAN_PBKDF_TUNING_TIME;
 
-   timer.run_until_elapsed(tune_msec, [&]() {
+   timer.run_until_elapsed(tune_time, [&]() {
       uint8_t output[32] = { 0 };
       scrypt(output, sizeof(output), "test", 4, nullptr, 0, N, r, p);
       });