RSA / ECB / OAEPWithSHA-256AndMGF1Padding但MGF1使用SHA-256？

Question

I found the hard way that in Oracle's Java standard crypto provider

Cipher cipher = Cipher.getInstance("RSA/ECB/OAEPWithSHA-256AndMGF1Padding");

uses MFG1 instanciated with SHA-1; SHA-256 is only used to hash the label (in practice empty). The only solution that I found to actually use SHA-256 in MFG1 (helped by that answer and comment ) was using an alternate form of Cipher.init :

cipher.init(Cipher.DECRYPT_MODE, privKey, new OAEPParameterSpec(
    "SHA-256", "MGF1", MGF1ParameterSpec.SHA256, PSource.PSpecified.DEFAULT
));

Question: is there a transformation that Cipher.getInstance will recognize, with effect similar to "RSA/ECB/OAEPWithSHA-256AndMGF1Padding" , except with MGF1 using SHA-256?

Answer 1

No, there isn't.

Java is open source. If unsure you can take a look at the sources for the OpenJDK.

In the init method of com.sun.crypto.provider.RSACipher it reads:

            spec = new OAEPParameterSpec(oaepHashAlgorithm, "MGF1",
                MGF1ParameterSpec.SHA1, PSource.PSpecified.DEFAULT);

I've checked this up to Java 8 update 60 for the OpenJDK. As you can see, you need to use the algorithm parameters.