Abstract: Main invention is methods and systems to create big and yet memorizable secret, which are later applied into many novel and innovated applications in information engineering. Among the big secret creation methods are (i) self-created signature-like Chinese character, (ii) two-dimensional key (2D key), (iii) multilingual key, (iv) multi-tier geo-image key, (v) multi-factor key using software token, and their hybrid combinations. Multihash key using hash iteration and hash truncation is further used to increase number of created secret for multiple offline and online accounts. Besides, multihash signature using multiple hash values of a message from different hash iteration provides object-designated signature function. The object may be recipient, action, feature, function, meaning, etc., as representation. Also, random space steganography using stego-data with random noise insertion is proposed.