Steganography in digital signal encoders
In a method for embedding steganographic information into the signal information of a signal encoder, a solution is to be created, which enables steganographic information being embedded into the signal information of a signal encoder such that a reduction of the voice quality is largely avoided. This is achieved by means of providing data information, particularly voice information, selecting steganographic information from a quantity of steganographic information, generating a code word from a code book provided by means of the signal encoder on the basis of the code elements forming the code book such that with the use of the code word generated within the scope of a transmission standard associated with the code book the data information is encoded into signal information containing the code word and/or making reference to the code word; and by the code word generated having an additional feature that can be calculated on the basis of the code elements forming the code word, wherein the additional feature represents the steganographic information.
1. A method for embedding steganographic information into signal information of a signal encoder, comprising:
providing data information, in particular voice information, as a signal to be coded;
selecting steganographic information as data to be embedded, wherein said steganographic information is selected from a set of steganographic information items; and
generating a code word from a provided algebraic code book using the signal encoder as a function of an algebraic construction rule based on the code elements forming the code word, so that:
(a) the data information is encoded, by using the generated code word within the scope of a transmission standard which can be associated with the code book, into signal information containing the code word or pointing to the code word, in the form of an encoded signal;
(b) the generated code word has an additional characteristic which can be calculated as a function of the code elements forming the code word, the additional characteristic representing the steganographic information; and
(c) the code book is sub-divided as a function of the algebraic construction rule into a set of sub-code books, and in each case only one code word associated with the sub-code book selected by the steganographic information to be current embedded is output by the signal encoder.
2. The method of claim 1 , further comprising evaluating the generated code word within the scope of the transmission standard which is associated with the code book by decoding the code word and subsequently comparing the decoded data information with the original data information.
3. The method of claim 2 , wherein the generating step takes into consideration a result of the evaluating step.
4. The method of claim 1 , wherein the encoder and code book are based on at least one of the GSM transmission standard and the UMTS transmission standard.
5. The method of claim 1 , wherein the generating step includes generating a code word as a function of one of the CELP coding, the ACELP coding, and the AMR coding.
6. The method of claim 1 , wherein the characteristic of the code word is calculated as the result of an application of at least one operation on at least one of the code elements forming the code word.
7. The method of claim 1 , wherein the code word implicitly fulfills the characteristic.
8. The method of claim 1 , wherein the step of selecting steganographic information includes selecting the steganographic information so that the steganographic information is used for improving the signal on the receiver side.
9. The method of claim 1 , wherein the step of selecting steganographic information includes selecting the steganographic information so that the steganographic information is used for at least one of an artificial bandwidth extension and a noise reduction on the receiver side.
10. The method of claim 1 , wherein the step of selecting steganographic information includes selecting the steganographic information so that the steganographic information is used as a digital watermark.
11. The method of claim 1 , further comprising transmitting the signal information either containing the code word or pointing to the code word for a receiver.
12. The method as claimed in claim 1 , further comprising providing data information on the receiver side by decoding the code word within the scope of the transmission standard.
13. The method of claim 11 , further comprising providing the steganographic information on the receiver side by calculating the additional characteristic of the code word as a function of the code elements forming the code word.
14. The method of claim 1 , wherein the method is utilized in a mobile radio device.
15. A signal encoder for embedding steganographic information into signal information of the signal encoder ( 100 ), characterized by
a first device for receiving data information, in particular voice information, as a signal to be encoded;
a second device for receiving steganographic information as data to be embedded, wherein the steganographic information is selected from a set of steganographic information items;
a third device for generating a code word from a provided algebraic code book using the signal encoder as a function of an algebraic construction rule based on the code elements forming the code word, so that:
(a) by using the generated code word within the scope of a transmission standard which can be associated with the code book, the data information is encoded into signal information containing the code word or pointing to the code word, in the form of an encoded signal; that
(b) the generated code word has an additional characteristic which can be calculated as a function of the code elements forming the code word, the additional characteristic representing the steganographic information; and
(c) the code book is sub-divided as a function of said algebraic construction rule into a set of sub-code books, and in each case only one code word associated with the sub-code book selected by the steganographic information to be currently embedded is output by the signal encoder.
16. The signal encoder of claim 15 , configured to provide the code word such that the code word implicitly fulfils the characteristic.
17. The signal encoder of claim 15 , wherein the third device is configured to generate the code word such that the code word already fulfils the characteristic which the steganographic information represents while it is being generated.
18. The signal encoder of claim 15 , configured to determine a first code element and a second code element of the code word, wherein the signal encoder determines the second code element as a function of the first code element and the information to be embedded.