nrf52 data encryption and decryption using ecc

[Jinesh]

Dear All,

I need to understand how the Asymmetric Encryption work in BLE.
From Nordic, I get to know the following that following are the nrf_crypto frontend modules

1. AES - Advanced Encryption Standard
2. AEAD - Authenticated Encryption with Associated Data
3. ChaCha-Poly
4. ECC - Elliptic Curve Cryptography
5. ECDH - Elliptic Curve Diffie–Hellman
6. ECDSA - Elliptic Curve Digital Signature Algorithm
7. EdDSA - Edwards-curve Digital Signature Algorithm
8. Hash - Cryptographic hash functions
9. HMAC - Hash-based message authentication code
10. HKDF - HMAC-based Extract-and-Expand Key Derivation Function
11. RNG - Random Number Generator

I get to know that using, NRF_CRYPTO_CURVES, we can generated private and Public keys,

Can you share me the Application Code, where I can see my data string get encrypt and decrypt using public and private key. 

Can anyone help me with maybe silly problem ?

Also please correct me, if any of my above understanding is wrong.

Thank you.

Regards,

Jinesh Punatar

[phone]

[Dmitry]

Hi Jinesh,

Are you interesting how asymmetric cryptography is implemented for LESC pairing in BLE, or you just want to encrypt some data with your own code?

In ECC cryptography, public and private keys are not used directly to encrypt data. Instead, each party generates its own key pair using nrf_crypto_ecc_key_pair_generate(), then both parties exchange with their public keys - that's called Diffie-Hellman algorithm, ECDH. Function nrf_crypto_ecdh_compute() takes own private key and other party's public key, the result is a shared secret (ECDH mathematic ensures that it will be the same at both sides). This shared secret is transformed to a session key with key derivation function (BLE uses HMAC-SHA-256 for this step), then session key is used to encrypt data with symmetric encryption algorithm (AES).
You can find examples for ECDH, HMAC and AES in SDK under examples/crypto/nrf_crypto.

[Jinesh]

Hi Dmity,

I am more interested in the example how we can encrypt and decrypt the data.with ECC - Elliptic Curve Cryptography method.