Cryptography – Communication system using cryptography
Reexamination Certificate
1998-06-30
2001-08-14
Peeso, Thomas R. (Department: 2766)
Cryptography
Communication system using cryptography
C380S029000, C380S028000
Reexamination Certificate
active
06275587
ABSTRACT:
BACKGROUND
This invention relates to secure communication techniques.
It is often desirable to transmit digital data from a source to one or more intended recipients in such a manner that the digital data can be recognized only by its intended recipients. Examples of instances where this is desirable include transmission of sensitive data (e.g., financial data, technical data, policy data) or software such as downloading an application program from the Internet, or retrieving a program or other data from a disk (e.g., optical or magnetic).
There are known techniques for secure data communication. Most of these techniques are classified as encryption/decryption techniques. In general, encryption techniques convert from one system of data formats to another sometimes by use of the source data to vary the conversion process. This conversion is performed in such a manner that given encryption information reconversion into the original form is possible by decryption.
A cryptographic transformation function takes data, e.g., symbols comprising a message in its original form, known as plaintext or plaintext symbols, and performs mathematical manipulations on the numerical representation of the message (either on a block or stream basis), transforming the message into ciphertext or cipertext symbols. Ciphertext is a representation of the original message which is unreadable, typically appearing as garbled text. Three types of cryptographic transformation functions which are used to convert plaintext to ciphertext are: secret key functions, public key functions, and hash functions.
Secret key functions employ directional encryption algorithms. A user selects a secret key which, along with the message to be encrypted, are the inputs to an algorithm. The resulting ciphertext is sent to a recipient where the recipient may be a person or a computer. To read the encrypted message, the recipient must know the user's secret key. Using the user's secret key and the ciphertext, as inputs to the same algorithm used to encrypt the message, the recipient is able to decrypt the message into plaintext and thus read the message sent by the user.
Encryption may also be accomplished by using a public key function. A public key function requires two keys, a public key and a private key for each user of the system. The public key for an individual user may be known by all other users of the system. The private key for the individual user should be known only by the individual user.
Hash functions unlike secret or public key are one-way encryption functions.
In the stream cipher technique, the symbols of the plaintext message are serially flowed through a stream ciphering system. The stream cipher system typically operates on the plaintext symbols using a key or random data to form a modulo sum.
SUMMARY
According to an aspect of the invention, a method includes encoding a serial bit stream of digital data by inserting bits of arbitrary value into bit positions of an encoded output unit along with a first number of bits from the serial bit stream. The method can also include decoding an encoded serial bit stream by selecting significant bits from a unit of the encoded bit stream that includes bits of arbitrary value.
According to a further aspect of the invention, a computer storage medium stores an encoded bit stream of digital data. The encoded bit stream include a header portion including encoding values used by a decoder to decode the encoded serial bit stream, a first set of portions of the encoded bit stream including bits of arbitrary value; and a second set of portions of the encoded bit stream including bits representative of an original input data stream.
According to a still further aspect of the invention, a method of encoding a serial bit stream of digital data, includes placing a first number of bits from the input bit stream into bit positions of an encoded output unit in accordance with a first value, said first number of bits aligned to a bit position in the encoded output unit in accordance with a second value and inserting bits of arbitrary value into remaining bit positions of the unit of the encoded output unit.
The bits of arbitrary value can be noise bits or bits from a second data stream. The bits can also be bits from a tail end of the serial bit data stream. The method iteratively generating a subsequent first value and subsequent second value for each action of placing a subsequent number of bits from the input bit stream into a subsequent encoded output unit. Generating the first value and the second value uses a deterministic non-trivial algorithm to select the first value and second value. The deterministic non-trivial algorithm can include determining pairs of generated values from a first prime number and a second prime number, where the first prime number is a primitive root of the second prime number.
According to a still further aspect of the invention, a method of decoding an encoded serial bit stream includes selecting significant bits from a unit of the encoded bit stream in accordance with a number of bits value and a bit alignment value to place the selected bits in a decoded bit stream.
The method gathers values of two prime numbers to produce generated values and generates the generated values based on the gathered values of the two prime numbers. The method produces the number of bits value and the bit alignment value from the generated values. The method iteratively generates values, produces the bit and alignment values and selects bits from the encoded bit stream until all bits of the encoded bit stream have been placed in the decoded bit stream.
According to a still further aspect of the invention, a computer program product resides on a computer readable medium. The product encodes a serial bit stream of digital data and includes instructions for causing a processor to place a first number of bits from the input bit stream into bit positions of an encoded output unit in accordance with a first value. The first number of bits are aligned to a bit position in the encoded output unit in accordance with a second value. The product also includes instructions to cause a computer to insert bits of arbitrary value into remaining, bit positions of the unit of the encoded output unit.
According to a still further aspect of the invention, a computer program product resides on a computer readable medium. The product can decode an encoded serial bit stream and includes instructions that cause a processor to select significant bits from a unit of the encoded bit stream in accordance with a number of bits value and a bit alignment value to place the selected bits in a decoded bit stream.
According to a still further aspect of the invention, a computer system includes a processor and a computer readable medium storing a computer program product for encoding a serial bit stream of digital data. The product includes instructions for causing the processor to place a first number of bits from the input bit stream into bit positions of an encoded output unit in accordance with a first value, said first number of bits aligned to a bit position in the encoded output unit in accordance with a second value and insert bits of arbitrary value into remaining, bit positions of the unit of the encoded output unit.
According to a still further aspect of the invention, a computer system includes a processor and a computer readable medium storing a computer program product for decoding an encoded serial bit stream. The computer program product includes instructions that cause a processor to select significant bits from a unit of the encoded bit stream in accordance with a number of bits value and a bit alignment value to place the selected bits in a decoded bit stream.
One or more of the following advantages may be provided by one or more of the aspects of the invention. The encoded bit stream has the original data inserted into random positions in the encoded output unit to obfuscate the original bits from the input bit stream. The encoded bit stream can have the input bit stream
Adobe Systems Incorporated
Fish & Richardson P.C.
Jack Todd
Peeso Thomas R.
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