i2d_ASN1_INTEGER zero pad

William Roberts bill.c.roberts at gmail.com
Tue Aug 6 16:00:49 UTC 2019

On Tue, Aug 6, 2019 at 10:56 AM Matt Caswell <matt at openssl.org> wrote:
> On 06/08/2019 16:34, William Roberts wrote:
> > Hi,
> > I occasionally get spurious errors in my ECDSA signatures, and it
> > appears that when the top byte is over 0x80 of either the R or S
> > component, that I get a zero pad. I noticed all this when reading
> > through the source, their was some comments (see below). I noticed a
> > d2i_ASN1_UINTEGER, but I can't find a coresponding i2d_ version to
> > create it. The zero pad seems to be the correct behavior, but it seems
> > to be breaking things.
> As you note the zero pad is the correct behaviour.
> > This is the link to the issue request I got filed for more details:
> > https://github.com/tpm2-software/tpm2-pkcs11/issues/277
> This seems to be a problem in tmp2-pkcs11 and not OpenSSL. So its not clear to
> me what your question to openssl-users is?

The questions is their is a d2i_ASN1_UINTEGER exists for that zero pad
issue, is their a i2d version, I couldn't find one.

I guess a second question is, is their a better way to build an ECDSA
signature from the R and S components, the code
for ASNI sequence is something I never figured out, is their an
example in ossl somewhere?

> Matt

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