RE: [EXT] [PATCH 11/40] cryptodev: remove asym crypto next xform

[Anoob Joseph <anoobj@marvell.com>]

Hi Arek, Akhil,

Please see inline.

Thanks,
Anoob

> -----Original Message-----
> From: Kusztal, ArkadiuszX <arkadiuszx.kusztal@intel.com>
> Sent: Wednesday, May 25, 2022 12:06 PM
> To: Akhil Goyal <gakhil@marvell.com>; dev@dpdk.org; Kiran Kumar
> Kokkilagadda <kirankumark@marvell.com>; Anoob Joseph
> <anoobj@marvell.com>
> Cc: Zhang, Roy Fan <roy.fan.zhang@intel.com>
> Subject: RE: [EXT] [PATCH 11/40] cryptodev: remove asym crypto next xform
> 
> 
> 
> > -----Original Message-----
> > From: Akhil Goyal <gakhil@marvell.com>
> > Sent: Wednesday, May 25, 2022 8:06 AM
> > To: Kusztal, ArkadiuszX <arkadiuszx.kusztal@intel.com>; dev@dpdk.org;
> > Kiran Kumar Kokkilagadda <kirankumark@marvell.com>; Anoob Joseph
> > <anoobj@marvell.com>
> > Cc: Zhang, Roy Fan <roy.fan.zhang@intel.com>
> > Subject: RE: [EXT] [PATCH 11/40] cryptodev: remove asym crypto next
> > xform
> >
> > > > > - removed asymnetric crypto xform next field.
> > > > > Rationale behind having chaining in symmetric crypto was a fact
> > > > > that encryption and authentication are usually done on the same
> > > > > set of data independent of algorithm.
> > > > > HW usually will be able to handle it in one PCI call.
> > > > > In asymmetric there is no such relation between algorithms,
> > > > > therefore next field would be useless.
> > > > >
> > > > > Signed-off-by: Arek Kusztal <arkadiuszx.kusztal@intel.com>
> > > >
> > > > Please check documentation "doc/guides/prog_guide/cryptodev_lib.rst"
> > > > Not all asymmetric crypto xforms are supported for chaining.
> > > > Currently supported asymmetric crypto chaining is Diffie-Hellman
> > > > private key generation followed by public generation.
> > > [Arek] And why do chaining when this can be done even with one bit flag.
> > >
> > I believe it is OK to remove next. @Kiran Kumar Kokkilagadda/Anoob
> > please confirm.
> >
> > If we are removing it, then documentation should be in sync.
> [Arek] - although, we may keep it for now, I am not dropping it in v2. DH priv +
> pub can be done with priv_key.len = 0 -> similar as 'k' in ecdsa when k.data =
> NULL.
> But I do not see any situation for now it will be  useful, it may be dropped later if
> not application found.
> >
> > > Also, currently API does not support chaining of
> > > > symmetric and asymmetric crypto xforms.
> > > [Arek] - This is one unlikely scenario to combine symmetric and
> > > asymmetric. One I can think of was once proposed DH + DSA
> > > integration for random number. But not much else, although we can
> > > keep it around for a
> > while.
> >
> > Yes it is highly unlikely to use this combination.

[Anoob] We may need this support when we add EdDSA support. That would involve a asymmetric operation after hash is generated (symmetric). 
https://en.wikipedia.org/wiki/EdDSA#Ed25519

And, asymmetric chaining may become useful when we have PMDs capable of doing more operations together (like the case with EdDSA). So my preference would be to retain the 'next' field in asym crypto xform.
 
> >
> > > >
> > > > > ---
> > > > >  lib/cryptodev/rte_crypto_asym.h | 2 --
> > > > >  1 file changed, 2 deletions(-)
> > > > >
> > > > > diff --git a/lib/cryptodev/rte_crypto_asym.h
> > > > > b/lib/cryptodev/rte_crypto_asym.h index 1652a434a5..b355cbe5fa
> > > > > 100644
> > > > > --- a/lib/cryptodev/rte_crypto_asym.h
> > > > > +++ b/lib/cryptodev/rte_crypto_asym.h
> > > > > @@ -492,8 +492,6 @@ struct rte_crypto_ecpm_op_param {
> > > > >   * Structure describing asym xforms.
> > > > >   */
> > > > >  struct rte_crypto_asym_xform {
> > > > > -	struct rte_crypto_asym_xform *next;
> > > > > -	/**< Pointer to next xform to set up xform chain.*/
> > > > >  	enum rte_crypto_asym_xform_type xform_type;
> > > > >  	/**< Asymmetric crypto transform */
> > > > >
> > > > > --
> > > > > 2.13.6