crypto_box(_open) confusion

[25A0]

I'm trying to use crypto_box and crypto_box_open to let party A encrypt and sign data for party B.
From my understanding, the following code should work:

def test_cross_box():
    pkA, skA = pysodium.crypto_sign_keypair()
    pkB, skB = pysodium.crypto_sign_keypair()
    nonce = pysodium.randombytes(pysodium.crypto_box_NONCEBYTES)
    msg = "foo"
    c = pysodium.crypto_box(msg, nonce, pkB, skA)
    d = pysodium.crypto_box_open(c, nonce, pkA, skB)
    assert msg == d

However, the above code raises a ValueError in
/usr/local/lib/python2.7/site-packages/pysodium/__init__.py:256: in crypto_box_open __check(sodium.crypto_box_open(msg, padded, ctypes.c_ulonglong(len(padded)), nonce, pk, sk))

The unit test only seems to check for cases where the public and secret key are the same when calling crypto_box and crypto_box_open, and indeed the following code works:

def test_self_box():
    pkA, skA = pysodium.crypto_sign_keypair()
    nonce = pysodium.randombytes(pysodium.crypto_box_NONCEBYTES)
    msg = "foo"
    c = pysodium.crypto_box(msg, nonce, pkA, skA)
    d = pysodium.crypto_box_open(c, nonce, pkA, skA)
    assert msg == d

Am I missing something about how crypto_box should be used, or is this a bug?

Using python 2.7, pysodium 0.6.8, libsodium 1.0.9

[stef]

would you try out crypto_box_keypair instead of crypto_sign_keypair, and check if it works like this?

[stef]

i'm not sure you should reuse the keys for encryption and signing. so you need two keys and also use crypto_sign_keypair not only crypto_box_keypair.

[25A0]

Thanks a lot! :)
Using crypto_box_keypair works flawlessly.
I admittedly didn't pay attention to the type of keypair I generated. Sorry for the noise