TLDR: WPA3-SAE - How does it work

• WPA3 - SAE - stands for simultaneous authentication of equals. This is a more secure mechanism than the previous WPA2-PSK [1].
• This relies on 3 fundamental components:
• DH - Diffie-hellman key exchange - Helps to generate a common shared key between the two WiFi entities e.g. station and client.
• ECC (elliptic curve cryptography) - Elliptic-curve cryptography (ECC) is an approach to public-key cryptography based on the algebraic structure of elliptic curves over finite fields. ECC allows smaller keys compared to non-EC cryptography (based on plain Galois fields) to provide equivalent security [2]. ECC is used once a common pairwise key is generated using the DH key exchange.
• Dragonfly key exchange is a mechanism for key exchange using discrete logarithm cryptography [3]. This is used with the two components above to setup SAE. See the reference for details on how it is setup [3]. Also covered in RFC7664.

labels: WiFi, TLDR, summary article, WPA3, SAE, security, 

Reference:

[1] WPA3-SAE Cisco Meraki reference

[2] Elliptic curve cryptography - Wikipedia

[3] Dragonfly key exchange in WPA3-SAE

(Programming) Combining the constant and volatile keywords in C

Sometimes asked as an interview question in embedded programming, this summary article covers an interesting use case of combining two seemingly opposite keywords in C [1].

Here is a TLDR of what this means:

1. int volatile x; Tells the compiler that x can change independent of the code e.g a register change that happens in Hardware.

2. uint16_t const x; Is used to tell the compiler that the variable x is immutable.

3. So when can we end up using these together? The article [1] talks about 3 cases, but they are essentially the same thing. We can use these keywords together for a pointer where the address of the pointer does not change (constant) but the value contained at that address is volatile (e.g. a register, shared memory etc). 

e.g. Constant address of volatile hardware register / memory. uint8_t volatile * const p_ptr; i.e the p_ptr has a constant address for a volatile (register).

 

Reference:

[1] Embedded.com. Michael Barr Combining C's volatile and constant 

[2] geeksforgeeks Volatile in C