Method of and apparatus for embedding data into an electronic document by modulating spaces between words
AssigneeOki Electric Industry Co., Ltd.
InventorsNaoharu Horino, Masayuki Suto, Kineo Matsui
Life of this patent
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Abstract
In a method of coding an electronic text document, the length of a space preceding a word in a line of text data of an electronic document relative to the length of a space following the word is modulated with the value of a bit of signature data. The signature data are thus embedded into the text data of the electronic document, not being easily discernible to illicit readers.
Claims12
A method of coding an electronic text document, comprising the steps of:
- preparing an electronic document carrying first text data including words forming a line with space between the words;
- preparing bits of second text data to be embedded in the electronic document;
- and
- modulating a ratio of a length of a first space preceding a word in a line of the first text data relative to a length of a second space following the word with a value of a bit of the second text data;
- whereby the second text data are embedded into the first text data.
A method of decoding an electronic text document carrying first text data including words forming a line with space between the words, with a length of a first space preceding a word in a line of the first text data relative to a length of a second space following the word forming a ratio which is modulated with a value of a bit of second text data, comprising the steps of:
- determining the ratio of the length of the first space preceding a word in a line of the first text data relative to the length of the second space following the word in the line of the first text data;
- and
- allotting a binary value on the basis of the ratio thus determined to form a bit of the second text data;
- whereby a series of the bits thus formed are representative of the second text data.
Apparatus for coding an electronic text document, comprising:
- a first memory for storing an electronic document carrying first text data including words forming a line with space between the words;
- a second memory for storing bits of second text data to be embedded in the electronic document;
- an encoder coupled to said first and second memories for modulating a ratio of a length of a first space preceding a word in a line of the first text data relative to a length of a second space following the word with a value of a bit of the second text data;
- and
- output means coupled to said encoder for reproducing the electronic document in which the second text data are embedded in the first text data.
Apparatus for decoding an electronic text document carrying first text data including words forming a line with space between the words, with a length of a first space preceding a word in a line of the first text data relative to a length of a second space following the word forming a ratio which is modulated with a value of a bit of second text data, comprising;
- input means for receiving the electronic text document;
- means coupled to said input means for determining the ratio of the length of the first space preceding a word in a line of the first text data relative to the length of the second space following the word in the line of the first text data;
- and
- means for allotting a binary value on the basis of the ratio thus determined to form a bit of the second text data;
- whereby a series of the bits thus formed are representative of the second text data.
Dependencies are inferred from the claim text.