Secure DTMF Signaling via Hexadecimal Padding and CRC
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Solution Overview
Problem
In non-3G communication systems, the lack of data connection with audio leads to unauthorized device authentication issues, DTMF tone distortion due to different codecs, and incomplete or incorrect telephone numbers being sent, resulting in erroneous calls between communication networks.
Innovation Solution
A DTMF encoding/decoding technique is introduced that pads bits in a specific manner, adds Cyclic Redundancy Check (CRC) and encryption to the DTMF tones, and converts DTMF characters into hexadecimal format using four-bit nibbles, ensuring error checking and authentication through unused bits and CRC bits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If DTMF tones are sent through audio packets without data connection, then compatibility with non-3G networks is maintained, but authentication security and error detection capability deteriorate
Solution Approach 1:
The patent merges authentication data, error detection codes, and DTMF signaling into a single integrated audio packet structure. By combining these functions that were traditionally separate into one unified format, the system achieves both security/reliability and compatibility with audio-only networks.
Solution Approach 2:
The audio packet is designed to serve multiple functions simultaneously: carrying DTMF tones for call setup, embedding authentication credentials, and including error detection capabilities. This multi-functionality allows a single packet type to work across different network types without requiring separate protocols.
2Use of energy by moving object
If lower bandwidth codecs are used for DTMF transmission, then bandwidth consumption is reduced, but DTMF tone recognition accuracy deteriorates
Solution Approach 1:
The patent applies preliminary error detection coding and authentication encoding to the DTMF signal before transmission. This preparatory processing ensures that even if the codec introduces distortion, the original signal can be accurately recovered and verified through the embedded check codes.
Solution Approach 2:
The patent implements feedback through embedded error detection codes that allow the receiving end to verify signal integrity. If distortion or errors are detected, the system can request retransmission or correct errors, ensuring accurate DTMF recognition despite bandwidth constraints.
3Device complexity
If DTMF digits are transmitted without error checking, then signaling simplicity is maintained, but call completion reliability deteriorates due to missing or incorrect digits
Solution Approach 1:
The patent combines error detection functionality with the existing DTMF signaling format by embedding check codes within the same audio packet structure. This integration adds reliability without requiring a completely separate error checking system or increasing overall signaling complexity.
Data Source
AI summary
A method and system for secure call Dual-Tone Multi-Frequency (DTMF) signaling includes entering (202) dial string of a telephone number of a destination device, assigning (210, 212) the dial string to a predefined string having a total length that is greater than the dial string such that there will be at least one leading hexadecimal bit in the predefined string length that is not used when the entered dial string is converted to a hexadecimal, converting (214) the dial string to hexadecimal, reversing the order of the hexadecimal, and placing the reversed hexadecimal at the beginning of the predefined string, appending (216) “one” bits to the predefined string length indicating how many nibbles of the predefined string length are unused, if any, and appending the remaining intervening unused bits in the predefined string length to “zero” bits, and sending (226) the encoded string length.