title: PIV Card Application Validation (PKCS #1 v.1.5 signature padding scheme)
body: <p>I am currently writing a .NET API for interacting with a smart card device using PC/SC.  I have most of the API working, but am really getting hung up on the General Authenticate Commands that the card can support.  I am trying to follow the process described in Appendix A.2 (page 25) of <a href="http://csrc.nist.gov/publications/nistpubs/800-73-3/sp800-73-3_PART2_piv-card-applic-card-common-interface.pdf" rel="nofollow">sp800-73-3_Part_2</a>.</p>
  
  <p>The issue I have is I don't understand what is meant by PKCS #1 v1.5 signature padding, or what the recommended approach would be for generating a challenge that abides by the format guideline.  Any guidance on generating this type of data would be appreciated (using existing .NET API's would be fantastic).</p>
  
  <p>Furthermore, is this format even required for the challenge?  I have tried just sending in a couple of randomly generated bytes but I received back a SW1/SW2 of 0x6A80 (incorrect reference data), so I do realize there are some structural requirements to the data.</p>