as far as is can see the RSA_2048 algorithm with OAEP padding use SHA1 as hash function.
Is there any possibility to use SHA2 ? Especially SHA256 ?
Yes, i can use RSA_2048 with no padding an do the padding by myself because the MessageDigest supports SHA256. But this would be a lot of work. For me it seems unusually that the cipher RSA algorithm does not have an implementation for SHA2 because in my opinion SHA2 is the most frequently used hash function.
Java Card API's are not always up to date. SHA2 support was only added in JC 2.2.2 (the current version I am using). Given JC3.0.1 API still only has one RSA algorithm with OAEP it is safe to assume it is still SHA1.