3.1.2.2 Look-Up Secret Verifiers

Before · SP 800-63B

After · SP 800-63B-4

Look-Up Secret Verifiers

Before · SP 800-63B

After · SP 800-63B-4

Verifiers of look-up secrets SHALL prompt the claimant for a secret from their authenticator. A secret from a look-up secret authenticator SHALL be used successfully only once. If the look-up secret is derived from a grid card, each grid cell SHOULD be used only once, which limits the number of authentications that can be accomplished using look-up secrets. A very long list of secrets is potentially required.

Verifiers SHALL store look-up secrets in a form that is resistant to offline attacks. All look- up secrets SHALL be stored in a hashed form using an approved hashing function.

Look-up secrets SHALL be at least six decimal digits (or equivalent) in length, as specified in Sec. 3.1.2.1 . Look-up secrets that are shorter than specified lengths have additional verification requirements as follows:

• Look-up secrets that are shorter than the minimum security strength specified in the latest revision of [SP800-131A] (i.e., 112 bits as of the date of this publication) SHALL be stored in a salted and hashed form using a suitable password hashing scheme, as described in Sec. 3.1.1.2 . The salt value SHALL be at least 32 bits in length and arbitrarily chosen to minimize salt value collisions among stored hashes. Both the salt value and the resulting hash SHALL be stored for each look- up secret.

• The verifier SHALL implement a rate-limiting mechanism that effectively limits the number of failed authentication attempts that can be made on the subscriber account, as described in Sec. 3.2.2 .

The verifier SHALL use approved encryption and an authenticated protected channel when requesting look-up secrets.