Is it Possible to Use Aead CCM (on a NRF 52840 with CC310) to verify a message without an encrypted Message? (Just Adata)

RE: Is it Possible to Use Aead CCM (on a NRF 52840 with CC310) to verify a message without an encrypted Message? (Just Adata)

DrGanmon — Mon, 15 Oct 2018 06:39:18 GMT

Thanks. That worked Out. i had an ADATA Offset form 1 Bit 🙄...

RE: Is it Possible to Use Aead CCM (on a NRF 52840 with CC310) to verify a message without an encrypted Message? (Just Adata)

Vidar Berg — Mon, 08 Oct 2018 13:23:01 GMT

Suggest that you run nrf_crypto_aead_crypt(&ccm_ctx, NRF_CRYPTO_ENCRYPT,..) first, then run decrypt you dummy data.

You can assume that the signature is invalid if you get internal error while all parameters are otherwise correct.

RE: Is it Possible to Use Aead CCM (on a NRF 52840 with CC310) to verify a message without an encrypted Message? (Just Adata)

DrGanmon — Mon, 08 Oct 2018 13:18:44 GMT

hi,

as writen in the comment ALL parameters are dummys. Even the MAC.

Does it mean i have no possibility to get if something with the input is wrong or the MAC was not correkt if i use the CC310?

RE: Is it Possible to Use Aead CCM (on a NRF 52840 with CC310) to verify a message without an encrypted Message? (Just Adata)

Vidar Berg — Mon, 08 Oct 2018 12:49:56 GMT

Hi,

I noticed that you initialize mac to 0xFF,.., you should to use the MAC generated when you "encrypted" the data (signed in this case). Note that the cc310 backends returns internal error if the signature validation fails so it doesn't necessarily mean that you passed an invalid arguments, etc.

RE: Is it Possible to Use Aead CCM (on a NRF 52840 with CC310) to verify a message without an encrypted Message? (Just Adata)

DrGanmon — Mon, 08 Oct 2018 09:03:22 GMT

the code i uses looks like:

uint8_t key[16] = {0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88, 0x99, 0xAA, 0xBB, 0xCC, 0xDD, 0xEE, 0xFF};
uint8_t nonce[13] = {0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88, 0x99, 0x00, 0x00, 0x00};
uint8_t mac[4] = {0xFF,0xFF, 0xFF, 0xFF}; // DEMO
uint8_t ret_buffer[20];
uint8_t auth[4] = {0xAA, 0xBB,0xCC,0xDD};
uint8_t adata[9]  = {0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88};
ret_code_t ret;


nrf_crypto_aead_info_t const * p_ccm_info = &g_nrf_crypto_aes_ccm_128_info;

ret = nrf_crypto_aead_init(&ccm_ctx, p_ccm_info, key);
APP_ERROR_CHECK(ret);

ret = nrf_crypto_aead_crypt(&ccm_ctx, NRF_CRYPTO_DECRYPT, nonce, sizeof(nonce), adata, sizeof(adata), auth,0, ret_buffer, mac, sizeof(mac));

printf(nrf_crypto_error_string_get(ret));