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

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Date: Fri, 16 Feb 2024 14:32:35 -0500
From: Stefan Berger <stefanb@...ux.ibm.com>
To: Simo Sorce <simo@...hat.com>, keyrings@...r.kernel.org,
        linux-crypto@...r.kernel.org, herbert@...dor.apana.org.au,
        davem@...emloft.net
Cc: linux-kernel@...r.kernel.org, saulo.alessandre@....jus.br
Subject: Re: [PATCH v2 00/14] Add support for NIST P521 to ecdsa and ecdh



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.
>