Re: [PATCH v2 00/14] Add support for NIST P521 to ecdsa and ecdh

[Stefan Berger]

On 2/16/24 14:27, Simo Sorce wrote:
> On Thu, 2024-02-15 at 18:13 -0500, Stefan Berger wrote:
> > This series of patches adds support for the NIST P521 curve to ecdsa and
> > ecdh. Test cases for NIST P521 are added to both modules.
> >
> > An issue with the current code in ecdsa and ecdh is that it assumes that
> > input arrays providing key coordinates for example, are arrays of digits
> > (a 'digit' is a 'u64'). This works well for all currently supported
> > curves, such as NIST P192/256/384, but does not work for NIST P521 where
> > coordinates are 8 digits + 2 bytes long. So some of the changes deal with
> > converting byte arrays to digits and digits to byte arrays.
> >
> >
> > Regards,
> >     Stefan
> >
> > v2:
> >   - Reformulated some patch descriptions
> >   - Fixed issue detected by krobot
> >   - Some other small changes to the code
> >
> > Stefan Berger (14):
> >    crypto: ecdsa - Convert byte arrays with key coordinates to digits
> >    crypto: ecdsa - Adjust tests on length of key parameters
> >    crypto: ecdsa - Extend res.x mod n calculation for NIST P521
> >    crypto: ecc - Implement vli_mmod_fast_521 for NIST p521
> >    crypto: ecc - For NIST P521 use vli_num_bits to get number of bits
> >    crypto: ecc - Add NIST P521 curve parameters
> >    crypto: ecdsa - Register NIST P521 and extend test suite
> >    x509: Add OID for NIST P521 and extend parser for it
> >    crypto: ecdh - Use properly formatted digits to check for valid key
> >    crypto: ecc - Implement ecc_digits_to_bytes to convert digits to byte
> >      array
> >    crypto: Add nbits field to ecc_curve structure
> >    crypto: ecc - Implement and use ecc_curve_get_nbytes to get curve's
> >      nbytes
> >    crypto: ecdh - Use functions to copy digits from and to byte array
> >    crypto: ecdh - Add support for NIST P521 and add test case
> >
> >   crypto/asymmetric_keys/x509_cert_parser.c |   3 +
> >   crypto/ecc.c                              |  71 +++++--
> >   crypto/ecc_curve_defs.h                   |  45 +++++
> >   crypto/ecdh.c                             |  59 +++++-
> >   crypto/ecdsa.c                            |  48 ++++-
> >   crypto/testmgr.c                          |  14 ++
> >   crypto/testmgr.h                          | 225 ++++++++++++++++++++++
> >   include/crypto/ecc_curve.h                |   3 +
> >   include/crypto/ecdh.h                     |   1 +
> >   include/crypto/internal/ecc.h             |  61 +++++-
> >   include/linux/oid_registry.h              |   1 +
> >   11 files changed, 495 insertions(+), 36 deletions(-)
>
> Hi Stefan,
> what kind of side-channel testing was performed on this code?
> And what is the use case you are adding it for?

We're using public keys for signature verification. I am not aware that
public key usage is critical to side channels.

The use case for adding it is primarily driven by closing a gap to 
complete the support for the common ECDSA NIST curves.

    Stefan

> Thanks,
> Simo.