How to get public key from private key in PKCS #11

[Martin Balao]

Hi Weijun,

I am not familiar to this algorithm but the typical key-exchange APIs 
let you generate a key pair first and, when you invoke the secret 
encapsulation mechanism, you use your private key + your counter-part 
public key. Do you think this could be the case here?

Regards,
Martin.-


On 12/10/24 00:07, Wei-Jun Wang wrote:
> So are you suggesting there is no such a way?
> 
> I do notice that in NSS’s own HPKE implementation, the receiver needs to 
> provide both keys [1]:
> 
> SECStatus PK11_HPKE_SetupR(HpkeContext *cx, const SECKEYPublicKey *pkR, 
> SECKEYPrivateKey *skR,
>                             const SECItem *enc, const SECItem *info);
> 
> Maybe they also don’t have a simple way to get pkR from skR.
> 
> Thanks,
> Weijun
> 
> [1] 
> https://github.com/nss-dev/nss/blob/e2f270997ff9364aebb688f49b7c28698b70f24d/lib/pk11wrap/pk11pub.h#L788 <https://github.com/nss-dev/nss/blob/e2f270997ff9364aebb688f49b7c28698b70f24d/lib/pk11wrap/pk11pub.h#L788>
> 
>> On Dec 9, 2024, at 21:27, Francisco Ferrari Bihurriet 
>> <fferrari at redhat.com> wrote:
>>
>> Hi Wei-Jun,
>>
>> As far as I know, public and private keys are different PKCS#11 objects,
>> each one with a different CK_OBJECT_HANDLE. See for example how
>> C_GenerateKeyPair [1] has two output parameters: CK_OBJECT_HANDLE_PTR
>> phPublicKey amd CK_OBJECT_HANDLE_PTR phPrivateKey.
>>
>> NSS uses CKA_PUBLIC_KEY_INFO only when wrapping [2] / unwrapping [3]
>> (C_WrapKey / C_UnwrapKey) RSA-PSS keys (where it stores an ASN1-encoded
>> SubjectPublicKeyInfo with the algorithm OID and the DER encoding of the
>> public key).
>>
>> Here [4] is how SunPKCS11 proceeds after calling C_GenerateKeyPair, by
>> creating two P11Key objects for each handle (P11PublicKey and
>> P11PrivateKey).
>>
>> [1]https://urldefense.com/v3/__https://docs.oasis-open.org/pkcs11/pkcs11-base/v3.0/pkcs11-base-v3.0.html*_Toc29976704__;Iw!!ACWV5N9M2RV99hQ!OmuwCcv-dJsqSgUuLEW8yqzvuB4Qwj5ay4afqgvAfvn3DiGx9lz31XjKDuAt_LABjdrwdCT8FmTTLO6ARjM$ <https://urldefense.com/v3/__https://docs.oasis-open.org/pkcs11/pkcs11-base/v3.0/pkcs11-base-v3.0.html*_Toc29976704__;Iw!!ACWV5N9M2RV99hQ!OmuwCcv-dJsqSgUuLEW8yqzvuB4Qwj5ay4afqgvAfvn3DiGx9lz31XjKDuAt_LABjdrwdCT8FmTTLO6ARjM$>
>> [2]https://urldefense.com/v3/__https://github.com/nss-dev/nss/blob/NSS_3_101_RTM/lib/softoken/pkcs11c.c*L6038-L6039__;Iw!!ACWV5N9M2RV99hQ!OmuwCcv-dJsqSgUuLEW8yqzvuB4Qwj5ay4afqgvAfvn3DiGx9lz31XjKDuAt_LABjdrwdCT8FmTT9ztKx9Y$ <https://urldefense.com/v3/__https://github.com/nss-dev/nss/blob/NSS_3_101_RTM/lib/softoken/pkcs11c.c*L6038-L6039__;Iw!!ACWV5N9M2RV99hQ!OmuwCcv-dJsqSgUuLEW8yqzvuB4Qwj5ay4afqgvAfvn3DiGx9lz31XjKDuAt_LABjdrwdCT8FmTT9ztKx9Y$>
>> [3]https://urldefense.com/v3/__https://github.com/nss-dev/nss/blob/NSS_3_101_RTM/lib/softoken/pkcs11c.c*L6604-L6605__;Iw!!ACWV5N9M2RV99hQ!OmuwCcv-dJsqSgUuLEW8yqzvuB4Qwj5ay4afqgvAfvn3DiGx9lz31XjKDuAt_LABjdrwdCT8FmTTdVw8oI8$ <https://urldefense.com/v3/__https://github.com/nss-dev/nss/blob/NSS_3_101_RTM/lib/softoken/pkcs11c.c*L6604-L6605__;Iw!!ACWV5N9M2RV99hQ!OmuwCcv-dJsqSgUuLEW8yqzvuB4Qwj5ay4afqgvAfvn3DiGx9lz31XjKDuAt_LABjdrwdCT8FmTTdVw8oI8$>
>> [4]https://urldefense.com/v3/__https://github.com/openjdk/jdk/blob/jdk-25*1/src/jdk.crypto.cryptoki/share/classes/sun/security/pkcs11/P11KeyPairGenerator.java*L424-L431__;KyM!!ACWV5N9M2RV99hQ!OmuwCcv-dJsqSgUuLEW8yqzvuB4Qwj5ay4afqgvAfvn3DiGx9lz31XjKDuAt_LABjdrwdCT8FmTTozigB-E$ <https://urldefense.com/v3/__https://github.com/openjdk/jdk/blob/jdk-25*1/src/jdk.crypto.cryptoki/share/classes/sun/security/pkcs11/P11KeyPairGenerator.java*L424-L431__;KyM!!ACWV5N9M2RV99hQ!OmuwCcv-dJsqSgUuLEW8yqzvuB4Qwj5ay4afqgvAfvn3DiGx9lz31XjKDuAt_LABjdrwdCT8FmTTozigB-E$>
>>
>> Regards,
>> --
>> Francisco
>>
>> On 12/10/24 01:43, Wei-Jun Wang wrote:
>>> Daniel suggested CKA_PUBLIC_KEY_INFO but it’s not available in NSS 3.101.
>>>
>>>> On Dec 9, 2024, at 08:07, Wei-Jun Wang <weijun.wang at oracle.com> wrote:
>>>>
>>>> Hi PKCS #11 gurus,
>>>>
>>>> DHKEM [1] requires a function
>>>>
>>>>  Pk(skX): The KEM public key corresponding to the KEM private key skX.
>>>>
>>>> "The notation pk(skX), depending on its use and the KEM and its
>>>> implementation, is either the computation of the public key using the
>>>> private key, or just syntax expressing the retrieval of the public
>>>> key, assuming it is stored along with the private key object."
>>>>
>>>> For the software side, I can calculate the public key [2] from the
>>>> private key. How can I do this in PKCS #11?
>>>>
>>>> Thanks,
>>>> Weijun
>>>>
>>>> [1]https://urldefense.com/v3/__https://www.rfc-editor.org/rfc/rfc9180.html*name-notation__;Iw!!ACWV5N9M2RV99hQ!OmuwCcv-dJsqSgUuLEW8yqzvuB4Qwj5ay4afqgvAfvn3DiGx9lz31XjKDuAt_LABjdrwdCT8FmTT0-STk6s$ <https://urldefense.com/v3/__https://www.rfc-editor.org/rfc/rfc9180.html*name-notation__;Iw!!ACWV5N9M2RV99hQ!OmuwCcv-dJsqSgUuLEW8yqzvuB4Qwj5ay4afqgvAfvn3DiGx9lz31XjKDuAt_LABjdrwdCT8FmTT0-STk6s$>
>>>> [2]https://urldefense.com/v3/__https://github.com/openjdk/jdk/blob/__;!!ACWV5N9M2RV99hQ!OmuwCcv-dJsqSgUuLEW8yqzvuB4Qwj5ay4afqgvAfvn3DiGx9lz31XjKDuAt_LABjdrwdCT8FmTTH8KrINU$ <https://urldefense.com/v3/__https://github.com/openjdk/jdk/blob/__;!!ACWV5N9M2RV99hQ!OmuwCcv-dJsqSgUuLEW8yqzvuB4Qwj5ay4afqgvAfvn3DiGx9lz31XjKDuAt_LABjdrwdCT8FmTTH8KrINU$>
>>>> adca97b659d725b0dd320322297dcbd1b443a047/src/java.base/share/classes/
>>>> sun/security/ec/ECPrivateKeyImpl.java#L209
>