Abstract: An authentication system comprises multiple servers and a controller coupled to or otherwise associated with the servers. The controller is configured to control storage in the servers of respective chaff sets or other types of value sets, each including at least one secret value obscured within a distinct arrangement of other values. Each of the servers comprises a local verifier configured to generate an indication as to whether or not a received input value corresponds to one of the values in its value set. The controller comprises a global verifier configured to authenticate the received input value based on the indications generated by at least a subset of the servers. By way of example, the secret value may comprise a common value which is the same for all of the value sets, with the value sets otherwise including distinct values such that their intersection yields only the common value.