hkdf

This tool is used to demonstrate how the HKDF expand and extract functions are derived from the HMAC and SHA256 cryptographic primitives.

This tool relies on the openssl command line utility.

Usage

  hkdf extract hexsalt hexkey
    - perform the HKDF-Extract function to concentrate key material
  hkdf expand hexprk hexinfo length
    - perform the HKDF-Expand function to generate keys
  hkdf expandlabel hexprk label hexcontext length
    - perform the HKDF-Expand-Label function as defined in RFC 8446 (TLS 1.3)

Examples

### example from TLS 1.3 of deriving a handshake secret

$ hkdf extract 00 0000000000000000000000000000000000000000000000000000000000000000
33ad0a1c607ec03b09e6cd9893680ce210adf300aa1f2660e1b22e10f170f92a

$ hkdf expandlabel 33ad0a1c607ec03b09e6cd9893680ce210adf300aa1f2660e1b22e10f170f92a \
  derived e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855 32
6f2615a108c702c5678f54fc9dbab69716c076189c48250cebeac3576c3611ba