Yubico Forum

Hi there,

I try to integrate HMAC-SHA1 challenge-response into one of my programs.
So I set my config #2 to HMAC-SHA1, variable size, NIST test key (3031..43)
My first experiments are with the 'Sample YubiClientAPI test container'.
When I set the PutBuffer to 'Sample #2' and press 'hmacSha1' I get a different result every time I press the button, but never the NIST vector (0922...) which I should get according to the document 'Yubikey Client COM API' Version 1.0.
What am I doing wrong?
Why is the result changing and not static?
Is the manual wrong or the software?
Thank you for your help

Josef

As there is only one buffer for both in- and out transaction, the input data must be written for each request. If sequential HMAC operations are performed, the input data is taken from the previous operation's out data and I guess that is why you experience this behavior.

In the sample client container, do the following steps:

1. Set data encoding to Ascii and click PutBuffer. The string "Sample #2" is written to the buffer

2. Set data encoding to hex (you can verify the data in hex by clicking GetBuffer, which then yields VT_BSTR 53616d706c65202332)

3. Check config #2

4. Press hmacSha1

5. The NIST string is displayed in the get field as VT_BSTR 0922d3405faa3d194f82a45830737d5cc6c75d24


The sample is maybe a bit unintuitive here so thanks for pointing this out. We shall update the manual.

Please let me know if this solved your problem.

Best regards,

JakobE
Hardware- and firmware guy @ Yubico

It works, thank you.
I also made the mistake to 'putbuffer' the NIST string in hex encoding.
One improvement of the test container could be, that it displays a warning if the user tries to 'putbuffer' something which is not valid according to the current data encoding.

Best regards,

Josef