US Patent 9386009 Secure identification string

Providing secure access to a mobile or other device using a network-assisted PIN or other short password is disclosed. In various embodiments, upon entry by a user of a personal identification number (PIN) or other short password, the password and a unique identifier, such as a user and/or device identifier, and/or other data, are sent to a remote server. The remote server returns to the mobile or other device a cryptographic key and/or other data, such as a more secure (e.g., more characters and/or including characters drawn from a larger set of characters) password usable at the mobile device to access encrypted data.