General Error when data length is more than 216 characters

[vizd...@gmail.com]

Hello Pkcs11Interop Team,
I am testing with SoftHSM2. I have created asymmetric keys through Pkcs11Admin and I am trying to use those keys in my test app.
I am using CKM_RSA_PKCS_OAEP for encryption. If the source data length is <= 216 bytes, it works fine. If more then is gives this exception

Exception: Method C_Encrypt returned CKR_GENERAL_ERROR
Pkcs11Interop
at Net.Pkcs11Interop.HighLevelAPI41.Session.Encrypt(Mechanism mechanism, ObjectHandle keyHandle, Byte[] data)

Following is the code snippet:

public byte[] Encrypt(string pin, string keyLabel, string _sourceData)
{
if (this._disposed)
throw new ObjectDisposedException(this.GetType().FullName);

if (_authenticatedSession == null)
{
_authenticatedSession = _slot.OpenSession(SessionType.ReadOnly);
}

byte[] encryptedData = null;
try
{
_authenticatedSession.Login(CKU.CKU_USER, pin);

//find our demo key
ObjectHandle generatedKey = FindKey(_authenticatedSession, keyLabel, CKO.CKO_PUBLIC_KEY);

byte[] sourceData = ConvertUtils.Utf8StringToBytes(_sourceData);

// Encrypt data
// Specify mechanism parameters
CkRsaPkcsOaepParams mechanismParams = new CkRsaPkcsOaepParams((ulong)CKM.CKM_SHA_1, (ulong)CKG.CKG_MGF1_SHA1, (ulong)CKZ.CKZ_DATA_SPECIFIED, null);

// Specify encryption mechanism with parameters
Mechanism mechanism = new Mechanism(CKM.CKM_RSA_PKCS_OAEP, mechanismParams);

encryptedData = _authenticatedSession.Encrypt(mechanism, generatedKey, sourceData);

}
catch (Exception)
{
throw;
}
finally
{
_authenticatedSession.Logout();
_authenticatedSession.Dispose();
_authenticatedSession = null;
}

return encryptedData;
}

private ObjectHandle FindKey(Session session, string keyName, CKO cko)
{
List<ObjectAttribute> objectAttributes = new List<ObjectAttribute>
{
new ObjectAttribute(CKA.CKA_CLASS, cko)
,new ObjectAttribute(CKA.CKA_LABEL, keyName)
};

session.FindObjectsInit(objectAttributes);
List<ObjectHandle> foundObjects = session.FindObjects(1);
session.FindObjectsFinal();
return foundObjects != null && foundObjects.Count > 0 ? foundObjects[0] : null;
}

What am I missing? Your help is greatly appreciated.

Thanks
Vishal Singh

[Jaroslav Imrich]

Hello Vishal Singh,

amount of data you can encrypt with RSA keys is limited. See my older answer to similar question at https://stackoverflow.com/a/22783225/3325704

Kind Regards

Jaroslav Imrich

https://jimrich.sk

jim...@jimrich.sk

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[vizd...@gmail.com]

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Thank you Jaroslav, that helped a lot. And thanks for making such an API.