thvdveld / cc2538-hal Goto Github PK

Branch: crypto

I am getting all-zero ciphertext when invoking the CCM routine on a plaintext that is less than 16 bytes. Looking at the CCM specification, it seems that padding needs to take place to round the lenght of the plaintext to 16-byte blocks. However, this seems to be working for plaintext sizes larger than 16 bytes. I couldn't find the place in the code where this is being done (possibly hardware is handling it?) so am opening this issue for reference.

Here is my minimal code snippet, excluding the boilerplate code:

    const P_3_TV:[u8; 10] = [0x2b, 0x48, 0x4c, 0xd5, 0x3d, 0x74, 0xf0, 0xa6, 0xed, 0x8b];
    let nonce = [
        0x00, 0x00, 0xf0, 0xe0, 0xd0, 0xc0, 0xb0, 0xa0, 0x00, 0x00, 0x00, 0x00, 0x05,
    ];
    let mut data_out = [0; 10];
    let mut tag = [0; 16];

    let ccm_info = AesCcmInfo::new(0, 2, 0).with_added_auth_data(&[]);
    aes_crypto.ccm_encrypt(
        &ccm_info,
        &IV_3_TV,
        &P_3_TV,
        &mut data_out[..],
        &mut tag[..],
    );

    rprintln!("data out: {:0x?}", data_out);

which gives the following output

data out: [0, 0, 0, 0, 0, 0, 0, 0, 0, 0]