CODEWITHSUNDEEP
encryptionrsaprivate-keypkcs#11
katika
katika

Reputation: 53

What is the mechanism of private key for decryption in PKCS11

Here is some part of my code

I already encrypt some text from another app VB.net via RSACryptoProvider

But I stuck at the step to decrypt in C.

Here is my code.

static CK_RV usePrivateKeytoDecrypt(CK_SESSION_HANDLE hSession, CK_OBJECT_HANDLE hObject) {
CK_RV rv = CKR_OK;
CK_MECHANISM mechanism = {
    {CKM_RSA_PKCS_OAEP}
};

rv = C_DecryptInit(hSession, &mechanism, hObject);

return rv;

}

The code is not completed. I try to debug and got the error CKR_MECHANISM_PARAM_INVALID

Please help. Thanks

Upvotes: 1

Views: 2594

Answers (3)

Libor B.
Libor B.

Reputation: 509

You must set mechanism parameters:

CK_RSA_PKCS_OAEP_PARAMS oaepParams = {CKM_SHA_1, CKG_MGF1_SHA1, 1, NULL_PTR, 0};
CK_MECHANISM MechEncrypt = {CKM_RSA_PKCS_OAEP, &oaepParams, sizeof(oaepParams)};

Upvotes: 1

mbuster
mbuster

Reputation: 170

You are not correctly initializing your mechanism structure. The CK_MECHANISM is a structure that requires 3 parameters to be defined:

typedef struct CK_MECHANISM {
  CK_MECHANISM_TYPE mechanism;
  CK_VOID_PTR       pParameter;
  CK_ULONG          ulParameterLen;  /* in bytes */
} CK_MECHANISM;

You need to initialize your mechanism as follow:

CK_MECHANISM  mechanism = { CKM_RSA_PKCS_OAEP, NULL_PTR, 0 };

If you generated your private-public key-pair as RSA key-pair (using CKM_RSA_PKCS_KEY_PAIR_GEN mechanism) e.g.

CK_MECHANISM  GenMechanism = { CKM_RSA_PKCS_KEY_PAIR_GEN, NULL_PTR, 0 };

Then you need to initialize your mechanism for decryption as follow:

CK_MECHANISM  mechanism   = { CKM_RSA_PKCS, NULL_PTR, 0};

I presume you are already logged in with your hsession and the hObject is the located private key to be used for decryption?

Upvotes: 1

always_a_rookie
always_a_rookie

Reputation: 4840

It depends on the algorithm of the Key Pair.

If the Key Pair's algorithm is RSA, it could be CKM_RSA_PKCS / CKM_RSA_PKCS_OAEP / CKM_RSA_X_509.

If the Key Pair's algorithm is EC, it could be CKM_ECDSA.

Provided, the Private Key has the attribute CKA_DECRYPT set to true.

You can refer to this documentation here.

Upvotes: 1

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