Question re attacking one (1) hash....!

[lechiffre]

I am trying to recover the message/string hashed by HMAC SHA-256. I am not as familiar with HMACs so this is where my confusion is centered. If I had only one SHA-256 hash, I don't think I could get much from it.

But let me explain:

The string which was hashed by HMAC SHA-256 authey is as follows: (E||PN||DH1||DH2)

I know the values of E, DH1, and DH2. [Actually DH1 and DH2 are the public DH keys between two network devices (one wishing to join, and the other authenticating through various steps to allow it).] What should make this rather easy is that the segment of the message I want (PN) is a number between 0000 and 9999.

I have played around with hashcat for the past few days....and a few years ago I had success with a file of SHA-1 hashes, so I know how hashcat works (or some of the features anyway), but of all my skills or areas of knowledge, working with hashes is a weak area (I know encryption...just not hashes). I have read the man pages and looked around the web, and what I would like to know is

1. I presume I can brute force this value...probably by first sticking this hash by itself in a file. But I am still unsure if this is possible since I only have this one hash. is this possible?

2. Would I need to construct any rules for this??? Again, I doubt it... but just wanted to check.

I know to most of you this is probably pretty simple... but I have read everywher and even bothered a few subs at Reddit, but I cannot get a decent answer...

Much appreciation in advance!!!

[epixoip]

If I understand correctly, you want to brute force both the key AND part of the message?

To approach this with hashcat you will need to generate 10000 possible messages, one for each possible value of PN. Then you will use each of these 10000 messages as the salt values with mode 1450.

Depending on the size of the message, you might be able to use Hashcat. However, based on the information you have provided, it seems like your message will be way too long for Hashcat. But even if it's not too long for Hashcat, if the key is long and random, it is very unlikely (read: impossible) that you will find the key.