Speech encryption method and device, speech decryption method and device

A speech encryption device for encrypting a digital speech signal, comprising:

• a first synchronous processing module configured to generate an encryption key, and to determine a corresponding shift parameter according to said encryption key;
• a first speech analysis module coupled electrically to said first synchronous processing module, and configured to derive a plurality of voice feature data from the digital speech signal, and to convert said voice feature data into converted speech data based on said shift parameter;
• and
• an encryption module coupled electrically to said first synchronous processing module and said first speech analysis module, and configured to determine corresponding dual-tone multi-frequency (DTMF) data according to said encryption key, and to interleave said DTMF data with said converted speech data so as to obtain a scrambled speech signal.