This is a follow up to Is It Possible To Reconstruct a Cryptographic Hash's Key
I am using a SHA-256 HMAC function on a single-word input: sha256hmac(privatekey,word) = output. The private key length is 128 bits, it does not change. The "word" is literally one short word.
Assuming an attacker knows "word" and "output" for multiple words (e.g., dog = "dsfwrw3r3r323211", cat = "3erwerwetwewer"):
- Is it significantly easier for an attacker to identify the private key by brute force with the above word/output pairs, as compared to a situation where they do not have those pairs?
- Is this brute force vulnerability (with word/output pair knowledge) an actual security concern?