1. A method for generating an encryption dictionary, the method comprises: generating a random value for each plaintext symbol of multiple plaintext symbols; and calculating a random token for each plaintext symbol based on a random value of the plaintext symbol and on random values of other plaintext symbols that have a lower lexicographic value than the plaintext symbol; wherein the calculating comprises applying a monotonic increasing function; wherein the encryption dictionary comprises a mapping between the multiple plaintext symbols and random token of the multiple plaintext symbols based on a sensitivity level of one or more of the symbols, wherein the random token for each plaintext symbol is based on a random value of the plaintext symbol and on random values of other plaintext symbols that have a lower lexicographic value than the plaintext symbol.