DH key agreement [rfc2631] is used to create a secret key using 1024 bit parameters of the standard IETF 'Second Oakley Group' [rfc2409]. The secret key is then digested into a 128-bit key appropriate for AES. This is done using HKDF [rfc5869] with NULL salt and empty info, using the SHA-2 256 hash algorithm [fips-180-3.2008]. The secrets are encrypted using AES [fips-197.2001] in cipher block chaining mode with pkcs7 style padding [rfc2315].

The public keys are transferred as an array of bytes representing an unsigned integer of arbitrary size, most-significant byte first (e.g., the integer 32768 is represented as the 2-byte string 0x80 0x00)