Apparatus and methods for protecting biometric authentication information associated with a paper document are provided. A mobile device application may pre-associate the document with a biometric input. The mobile device application may generate a first composite hash value based on a combination of a numerical representation of a first image of the paper document and a numerical representation of a first biometric input. Subsequently, an authentication server may generate a second composite hash value based on a combination of a numerical representation of a second image of the paper document and a numerical representation of a second biometric input. The authentication server may determine whether an edit distance separating the second composite hash value and the first composite hash value is less than a threshold distance. If the edit distance is less than a threshold distance, the paper document may be authenticated.