Data type preserving encryption

A method encrypting characters from a data element in a database, the method comprising:

• reading information identifying a data type associated with data in a particular column of the database from a location in the database, the location being outside the particular column;
• reading a data element from the particular column, the data element including a first character string;
• associating an index value with each character in the first character string;
• defining an initial value by hashing an encryption key;
• creating a second character string formed by replacing each character in the first character string with the character's associated index value;
• replacing each index value in the second character string with a result obtained from the steps of:
• adding adjacent index values pairwise from the left to the right using the initial value when adding the leftmost character to obtain a first shift result;
• adding to the first shift result adjacent index values pairwise from the right to the left using the initial value when adding the leftmost character to obtain a second shift result;
• and
• adding to the second shift result a varying value;
• encrypting the second character string wherein each character in the encrypted second character string is a valid member of the identified data type associated with the data element, where said encrypting includes converting encrypted replaced index values to characters;
• and
• storing the encrypted second character string at the particular column of the first character string in the database.