Slow RSA Decryption

VCL TMS Cryptography Pack
1

Hello,

we are using the following code to decrypt a string with 39 characters (encrypted to 346 characters as base 64). Decrypting takes over 1 second. Using the TMS Cryptography Pack demo it's slow, too.
When using it in one of our containers which doesn't have a lot of performance it takes up to 40 seconds.
We also tried setting "withOpenSSL := true" and using "FromOpenSSLPrivateKey" with the same result.
When we use openssl.exe as a command line it takes about 10 to 20 miliseconds.

Is there a reason why it is so slow if the use TRSAEncSign? Any way to increase the speed? Did we use any wrong settings?
We need to use "epkcs1_5" in this case but also tried using oaep with no change in speed.

FRSAEnc := TRSAEncSign.Create(nil);
FRSAEnc.keyLength := kl2048;
FRSAEnc.outputFormat := base64;
FRSAEnc.Unicode := yesUni;
FRSAEnc.encType := epkcs1_5;
FRSAEnc.FromPrivateKey(PrivKey);
var decrStr := FRSAEnc.Decrypt(Request.Headers.Get('Key'));

2

Hi,
RSA is slow in full Delphi mode (I think it's mentioned in the manual). It is due to at least 3 things: lots of checks, data structures and Delphi that is slower than C (the library was written in C up to 4.3, with Delphi wrappers).
I'll improve that in future releases but it will never be as fast as C code.
Regards,
bernard

3

Hi,
I am working on improving RSA, which is not granted without a major rewrite (so not now).
Just for you to know that running 64 bit tests is about 30% faster than runining identical tests in 32-bit mode on Windows.
Regards,
bernard

4

Hi,
I made a few changes in RSA that will appear in the next release.

Here is a simple benchmark on Windows, OSX and OSX ARM for 100 PKCS encryptions and decryptions with a 2048 bit key. 100 is for the fastest implementation (the key is generated before).

Windows 64: 100 ( i9-9880H CPU @ 2.30GHz) (~0.6 s per encryption/decryption sequence)
Windows 32: 150
OSX 64: 160 (2014 MacBook Air, i7 CPU @ 1.7 GHz)
OSX ARM (M1 Max): 140

For 4096 bit keys, multiply all results by ~4.

Conclusion: W32 is much slower than W64 and the M1 chip is a bit disappointing.

Regards,
bernard

1 Like
5

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