See this example where it stores the "salt" for an RC4 key:
algCrypt : 00006801 - 26625 (CALG_RC4)
dwAlgCryptLen : 00000028 - 40
dwSaltLen : 00000010 - 16
pbSalt : 7714b66f32c090777c36d5fbc7f123c3
dwHmacKeyLen : 0000000b - 11
pbHmackKey : 1dee397af8bf2f227d7940
the pbHmackKey member actually stores the AUX_INFO for the algorithm above. See the pvEncryptionAuxInfo section of https://learn.microsoft.com/en-us/windows/win32/api/wincrypt/ns-wincrypt-crypt_encrypt_message_para for details.
See this example where it stores the "salt" for an RC4 key: algCrypt : 00006801 - 26625 (CALG_RC4) dwAlgCryptLen : 00000028 - 40 dwSaltLen : 00000010 - 16 pbSalt : 7714b66f32c090777c36d5fbc7f123c3 dwHmacKeyLen : 0000000b - 11 pbHmackKey : 1dee397af8bf2f227d7940