AES ECB decryption on nRF52832 with SDK 14.2

[patjshan]

Hi All,

I am trying to decrypt some data coming in on my board with AES ECB mode. I know that there is no decryption function for ECB and you have to use the same sd_ecb_encrypt function and XOR the resulting ciphertext with the encrypted data. My question is that if I'm not using a nonce or counter value (i know i should be using them to make it more secure but i'm not at that step yet) what should I populate the ECB data structure's cleartext field and do I need to XOR the result with something?

Setup: nRF52832, SDK 14.20, SD V5

Further Background: I'm using code based on this Nordic post on ECB AES mode but the example uses ECB as part of a stream cipher; i need to use it strictly as a block cipher.

If you'd like any further information from me let me know,

Thanks,

patjshan

[Einar Thorsrud]

Hi,

It is not clear to me exactly how the data you need to decrypt is encrypted, and AES ECB can be used in several ways. Note that the ECB peripheral does not do encryption in HW (see ECB peripheral documentation), but that may not be a problem, depending on how you intend to use it.