paymentmethodtoken in python

[Bastien-BO]

Help us help you

I'm working for a PSP and curently trying to add Gpay support for a python backend.

Is your feature request related to a problem?

The gpay doc ask to use tink to handle keysets and messages encryption/decryption with paymentmethodtoken. The only integration of it that i found is in java.

Describe the solution you'd like

Having a equivalent of paymentmethodtoken in Python.

Describe alternatives you've considered

Additional context

[thaidn]

Have you tried https://github.com/google-pay/tink-jni-examples/tree/master/TinkJNIPython?

[Bastien-BO]

@thaidn thanks for your reply,

I didn't know this package exist, thanks for it. Sadly since it's a bridge to the java lib i'm not going to use it.

I'm curently making my own lib that use simple python with PyCryptodome

[thaidn]

If you can share the code, I can help you review it.

On Wed, Nov 17, 2021 at 11:19 AM Bastien Bouchoux @.***> wrote:

@thaidn https://github.com/thaidn thanks for your reply,

I didn't know this package exist, thanks for it. Sadly since it's a bridge to the java lib i'm not going to use it.

I'm curently making my own lib that use simple python with PyCryptodome

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[Bastien-BO]

thanks

i have to finish it first so hopefully in a week or two :+1:

[Bastien-BO]

in my quest of writing this lib I'm facing an issue with the message decryption part.

to give you more insight to were i am:

Verify intermediate signing key => done Verify payload signature => done Decrypt payload content => doing

I have a hard time understanding what operations are done in the encryptedMessage decryption process. My understanding is that this process start with decrypt:

private String unsealECV2(String sealedMessage) throws GeneralSecurityException {
    JsonObject jsonMsg = JsonParser.parseString(sealedMessage).getAsJsonObject();
    validateECV2(jsonMsg);
    String signedMessage = verifyECV2(jsonMsg);
    String decryptedMessage = decrypt(signedMessage);
    validateMessage(decryptedMessage);
    return decryptedMessage;
  }

Is that true or am i totaly missing the actual way it works ? I'm a bit confuse about kem and dem, i don't understand what they are doing.

[morambro]

Closing this due to inactivity. Please reopen this issue in https://github.com/tink-crypto/tink-py/issues if you have further questions/follow-up comments.