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driver-only-builds: update EC and FFDH sections

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Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
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Valerio Setti 2023-08-15 10:59:58 +02:00
parent 307810babb
commit d31b28485b
1 changed files with 32 additions and 7 deletions
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39
docs/driver-only-builds.md
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@ -76,10 +76,6 @@ TODO
Elliptic-curve cryptography (ECC)
---------------------------------
Note: things are still evolving. This section describes the situation right
after #7452 has been merged. It will be updated again in #7757 when bignum is
done.
It is possible to have most ECC operations provided only by a driver:
- the ECDH, ECDSA and EC J-PAKE algorithms;
- key import, export, and random generation.
@ -107,6 +103,11 @@ without `MBEDTLS_ECP_C` provided the corresponding
RSA or FFDH, then you can also disable `MBEDTLS_BIGNUM_C` for further code
size saving.
[Coming soon] As noted in the "Limitations regarding the selection of curves"
section below, there is an upcoming requirement for all the required curves to
be also accelerated in the PSA driver in order to exclude the builtin algs
support.
### Limitations regarding fully removing `ecp.c`
A limited subset of `ecp.c` will still be automatically re-enabled if any of
@ -144,10 +145,34 @@ timeline, please let us know if you're interested.
### Limitations regarding the selection of curves
TODO: apparently we don't really support having some curves built-in and
others driver-only... investigate and describe the situation. See also #7899.
There is an ongoing work which tries to establish a link/constrain between
the list of supported curves and supported algorithms both in builtin and PSA
sides. In particular:
- #8014 ensures that the curves supported on the PSA side (`PSA_WANT_ECC_xxx`)
are always a superset of the builtin ones (`MBEDTLS_ECP_DP_xxx`)
- #8016 forces builtin alg support as soon as there is at least one builtin
curve. In other words, in order to exclue all builtin algs, all the required
curves should be supported and accelerated by the PSA driver.
Finite-field Diffie-Hellman
---------------------------
TODO
Support is pretty similar to the "Elliptic-curve cryptography (ECC)" section
above.
Key management and usage can be enabled by means of the usual `PSA_WANT` +
`MBEDTLS_PSA_ACCEL` pairs:
- `[PSA_WANT|MBEDTLS_PSA_ACCEL]_KEY_TYPE_DH_PUBLIC_KEY`;
- `[PSA_WANT|MBEDTLS_PSA_ACCEL]_KEY_TYPE_DH_KEY_PAIR_BASIC`;
- `[PSA_WANT|MBEDTLS_PSA_ACCEL]_KEY_TYPE_DH_KEY_PAIR_IMPORT`;
- `[PSA_WANT|MBEDTLS_PSA_ACCEL]_KEY_TYPE_DH_KEY_PAIR_EXPORT`;
- `[PSA_WANT|MBEDTLS_PSA_ACCEL]_KEY_TYPE_DH_KEY_PAIR_GENERATE`;
The same holds for the associated algorithm:
`[PSA_WANT|MBEDTLS_PSA_ACCEL]_ALG_FFDH` allow to build accelerating FFDH and
removing builtin support (i.e. `MBEDTLS_DHM_C`).
### Limitations
Support for deterministic derivation of a DH keypair
(i.e. `PSA_WANT_KEY_TYPE_RSA_KEY_PAIR_DERIVE`) is not supported.