How do I define a pkcs11 attribute for a RSA private key that can store metadata like IV or date of generation used to the key?

Question

According to the latest PKCS#11 spec the typical attribute structure of a RSA private key is the following:

CK_ATTRIBUTE template[] = {
{CKA_CLASS, &class, sizeof(class)},

{CKA_KEY_TYPE, &keyType, sizeof(keyType)},

{CKA_TOKEN, &true, 1},

{CKA_LABEL, label, sizeof(label)},


{CKA_SUBJECT, subject, sizeof(subject)},

{CKA_ID, id, sizeof(id)},

{CKA_SENSITIVE, &true, 1},

{CKA_DECRYPT, &true, 1},

{CKA_SIGN, &true, 1},

{CKA_MODULUS, modulus, sizeof(modulus)},

{CKA_PUBLIC_EXPONENT, publicExponent, sizeof(publicExponent)},

{CKA_PRIVATE_EXPONENT, privateExponent, sizeof(privateExponent)},

{CKA_PRIME_1, prime1, sizeof(prime1)},

{CKA_PRIME_2, prime2, sizeof(prime2)},

{CKA_EXPONENT_1, exponent1, sizeof(exponent1)},

{CKA_EXPONENT_2, exponent2, sizeof(exponent2)},

{CKA_COEFFICIENT, coefficient, sizeof(coefficient)}

};

However, there is another attribute CK_VALUE that can only be used for creating pkcs 'data objects' and NOT 'key objects'. When I use this field CK_VALUE to create key objects PKCS throws me an invalid attribute error. I would like to use a similar field in the which contains a string formatted value that can hold metadata information related to the key (like IV used to wrap the RSA key, date of generation of the key, etc). Is there a way to store these information in the existing pkcs11 template without tinkering with the attribute data structure in the implementation? I am using OpenDNSSec community's SoftHSM n2.0 package for the pkcs implementation.

Any suggestions would be appreciated.