0

Microsoft says:

The CryptEncrypt function is not guaranteed to be thread safe and may return incorrect results if invoked simultaneously by multiple callers.

Does this mean that the function modifies global data?
Or does it simply mean that you can't use the same hash/key simultaneously?

(In other words, is the comment below correct?)

user541686
  • 205,094
  • 128
  • 528
  • 886

2 Answers2

1

It means what it means: the function is not guaranteed to be thread-safe. It probably has an internal static (or global) state, but that's an implementation detail.

Whether you use or not the same hash or key is irrelevant.

Edit after comment: according to this MSDN page, CryptoApi key handles are not thread safe because of the internal key state:

Most algorithms and modes require that data be decrypted in the same order that it was encrypted. This is a difficult task in a multithreaded environment because use of a critical section will not address the ordering issue. If you are using a block cipher (that is, RC2, DES, or 3DES) in ECB cipher mode, then this issue is not a factor because the internal key state does not change. However, ECB is not the default cipher mode. CBC is the default cipher mode. With CBC cipher mode, the internal key state does change.

So after all, it would seem reasonable to think that you can indeed use CryptEncrypt on several threads if they don't share the same key. This is merely a guess, though.

user703016
  • 37,307
  • 8
  • 87
  • 112
0

I believe it means that you cannot fork several processes at the same time to use it because the function uses shared address space. It has access to the memory of all the threads and therefore will give you unexpected results. This should only be a problem with multi-threading if your application is doing that.

Shawn
  • 3,583
  • 8
  • 46
  • 63