Systems for embedding information in data strings

A computer-implemented method for encrypting and embedding information in a data string containing characters in a first set of characters, comprising:

• encoding, with a computing device, the data string using at least one index of sequential index values each of which corresponds to a respective one of the characters in the first set of characters to produce an encoded data string;
• encrypting, with the computing device, the encoded data string using format-preserving encryption to produce an encrypted encoded data string;
• and
• embedding, with the computing device, information in the encrypted data string to produce an augmented encrypted encoded data string;
• using, with at least one of the computing device and an additional computing device, at least one additional index of sequential index values each of which corresponds to a respective one of characters in a second set of characters to decode the augmented encrypted encoded data string to produce an augmented encrypted data string that contains characters in the second set of characters, wherein the second set of characters has a greater number of characters than the first set of characters, wherein the first set of characters has only numerical characters, wherein the second set of characters has numerical characters and letter characters, and wherein the at least one additional index of sequential index values is different from the at least one index of sequential index values with which the data string was encoded.