Title: An Easy Method to Implement Audio Cryptography Schemes without Computing Devices
1An Easy Method to Implement Audio Cryptography
Schemes without Computing Devices
- Shin Yan Chiou and Chi Sung Laih
- Department of Electrical Engineering,
- Director, Computer and Communication Network
Center, - National Cheng Kung University, Tainan, TAIWAN
- Republic Of China
2Contents
Preview Works (DHQ and DLQ ACS)
Easy Audio Cryptography Scheme
Comparison
3Introduction of ACS
- A secret sharing scheme
- A method to hide a message into n sounds
- Perceive the message by ears by playing t of the
n sounds simultaneously - Similar to Visual Secret Sharing Scheme but use
ears instead of eyes to perceive the secret
4Previous Works
- DHQ Audio Cryptography Scheme(Desmedt, Hou
Quisquater, Asiacrypt98) - DLQ Audio Cryptography Scheme(Desmedt, Le
Quisquater, Proceedings of Info Hiding99)
5DHQ ACS
- Wave based (2, 2) audio crypto scheme.
- In phase to be secret 1 and out of phase to be
secret 0 - A (2, n) scheme needs ?lon2n? different sounds
6A DHQ (2, 2) instance
M (0 0 1 1)
7Disadvantages of DHQ ACS
- Low contrast when secret perceiving
- ?lon2n? cover sounds are needed for (2, n) scheme
- Precise synchronization is needed
- When secret hiding, a computing device is needed
8DLQ ACS
- A sort of (2, 2) ACS
- Nonbinary Audio, such as human speech, can be
perceived. - To hide the secret by embedding the preshares
into a covering signal to be shares - To perceive the secret by both using a mixer to
eliminate the covering signal and a amplifier to
amplify the message synthesized by two shares (or
preshares)
9Disadvantages of DLQ ACS
- ?lon2n? cover sounds are needed for (2, n) scheme
- Precisely synchronization is needed
- When secret hiding, a special computing device is
needed - When secret perceiving, some special devices such
as a mixer and a amplifier are needed
10The proposed Easy Audio Cryptography Scheme
11- Definition 1 and are n ?
1 Matrices representing bit 0 and bit 1
respectively, where the notation ?k, 1 ? k ? n,
denotes the sound k which is the kth sound of
the given n sounds.
12- Construction Assume the m-bit secret message M
M1, M2, , Mm Mj ?0, 1. Let BL and BH be
Matrices specified in Definition 1 and Sn?m
sij B1B2Bm be an n ? m Matrices
whereThen the n shares are constructed by
recording the sound sij into the jth sound of
the ith share for all i and j.
13- Reconstruction Let two shares be Si si1,
si2, , sim and Sj sj1, sj2, , sjm i ? j.
Then - By playing any two of the constructed n shares
simultaneously, then the kth bit would be bit 1
if the two of the kth sound of the two shares are
different and would be bit 0 if they are the same.
14Example 1 (Different Sounds)
????
Rhythm X
? ???
Rhythm Y
?
?
? ?
Rhythm XY
?
?
0 1 0 1
? Message
15Example 2 (General Sentences)
Rhythm X
My number is 4441234. -- Please call me. --
Rhythm Y
My number is 8885678. -- Please call me. --
1 0 1 0
? Message
16Comparison
Item Method Contrast Band Width Cover Sound n?BW Precisely Synchronize Computing Device Cost
DHQ Low Low ?lon2n? ? ? ? Yes Yes Middle
DLQ - High ?lon2n? ? ? ? Yes Yes High
Proposed High Middle 0 indep No No Low
- Note
- n?BW relationship between n and bandwidth
- IP inverse proportion