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  Random number generation for encrypting cellular communicationsUSPTO Application #: 20070014401Title: Random number generation for encrypting cellular communications Abstract: In wireless communications, transmission devices require continuous supplies of random data for encryption processes. The invention provides a method for generating a continuos pool of truly random data with hardware that is already available in conventional CDMA phones. (end of abstract) Agent: Qualcomm Incorporated - San Diego, CA, US Inventor: SANDIP SARKAR USPTO Applicaton #: 20070014401 - Class: 380046000 (USPTO) Related Patent Categories: Cryptography, Key Management, Having Particular Key Generator, Nonlinear (e.g., Pseudorandom) The Patent Description & Claims data below is from USPTO Patent Application 20070014401. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] I. Field of the Invention [0002] The current invention relates to wireless communications networks. More specifically, the present invention relates to a novel and improved method of generating random data for the purpose of encrypting transmissions in wireless communications systems. [0003] II. Description of the Related Art [0004] Encryption schemes for wireless communications require continuous pools of random data. There are a number of ways to generate bits with good spectral properties through software. However, any software produced random number must be pseudo-random by its very nature rather than truly random, as all number sequences generated by software are periodic. Such psuedo-random sequences are susceptible to being deciphered by a third party. Only hardware generated data can be mathematically random. Although other techniques such as employing the voltage jitter from key presses or the time delay between key presses are known, the present invention has significant advantages over these techniques which are either pseudo-random or do not supply continuous random data. [0005] Presently, there is no ideal method of continuously generating a sufficient supply of truly random data from existing wireless phone hardware for encrypting wireless communications. SUMMARY OF THE INVENTION [0006] The present invention is a novel and improved method for generating a continuous pool of random data bits for wireless communications encryption by employing hardware that is already available in conventional wireless phones. In particular, the present invention uses the random nature of the propagation path and the receiver front end, and their effect on the received signal characteristics, to generate a set of random numbers. The present invention is described in terms of a CDMA wireless phone, but the principles are readily adapted to other wireless modulation techniques. BRIEF DESCRIPTION OF THE DRAWINGS [0007] The features, objects, and advantages of the present invention will become more apparent from the detailed description set forth below when taken in conjunction with the drawings in which like reference characters identify correspondingly throughout and wherein: [0008] FIG. 1 is a high level flowchart diagram of the random data collection method of the present invention. [0009] FIG. 2 is a simplified diagram of a partial CDMA phone signal path through CDMA hardware apparatus. [0010] FIG. 3 is an apparatus diagram of a Receive Automatic Gain Control Circuit. [0011] FIG. 4. is an apparatus diagram of an I/Q DC Offset Correction Loop. [0012] FIG. 5 is an apparatus diagram of a Time Tracking Loop. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS [0013] FIG. 1 shows a high level overview of the exemplary method for generating a pool of random data, often required for encryption, from common CDMA phone hardware. The method is readily amended by omission or re-ordering of the steps illustrated and without departing from the scope of the present invention. The present invention is described in the context of CDMA phones. However, the present invention will be equally applicable to other modulation techniques. [0014] In current CDMA systems, data is transmitted in 20 millisecond frames. The method of the present invention is capable of producing four random data bits for each frame, equal to 20 milliseconds, using CDMA variables available during a normal phone call. The invention generates the data from truly random sources present in the received signal. These generated random data bits are collected in a random data pool and made available to encryption processes. [0015] In block 100, in the exemplary embodiment, the Receive Automatic Gain Control (AGC) circuit of the CDMA phone is employed to generate two random bits of data every 20 milliseconds. Generation of random bits from the Receive AGC circuit is described in detail in FIG. 3. The Automatic Gain Control element is employed in wireless phones to keep the in-band energy presented to the demodulator at a fixed level. The received in-band energy fades in a random fashion due to changes in the propagation path from shadowing, fading and multi-path phenomenon. The received signal is normalized by means of a variable gain amplifier of the AGC to provide a first set of random bits. Because the gain of the variable gain amplifier varies continuously, one skilled in the art will understand that the random variable may be extracted at an arbitrary rate from the AGC. Moreover, more or less than two bits may be extracted in the random number generator. [0016] In block 102, in the exemplary embodiment, the In Phase (I)/Quadrature Phase(Q) DC Offset Correction Loop of the CDMA phone is employed to generate one random data bit every 20 milliseconds. Generation of random bits from the DC Offset Correction Loop is described in detail in FIG. 4. The DC Offset Correction Loop element is employed in wireless phones to correct a small DC offset introduced to the received signal during analog to digital conversion 206. The DC offset is added to the digital signal in a random fashion due to effects of the conversion process on analog signal characteristics. The DC Offset Correction Loop normalizes the mean DC value of the converted signal to zero by means of gain amplification and summing, to provide an additional random bit. Because the DC offset varies continuously, one skilled in the art will understand that the random variable may be extracted at an arbitrary rate from the DC Offset Correction Loop. Moreover, more or less than one bit may be extracted in the random number generator. [0017] In block 104, in the exemplary embodiment, the Time Tracking Loop of the CDMA phone is employed to generate one random bit every 20 milliseconds. Generation of random bits from the Time Tracking Loop is described in detail in FIG. 5. The Time Tracking Loop element is employed in wireless phones to maintain bit synchronization regardless of fluctuations in propagation path delays. Propagation path delays vary in a random fashion due to changes in the propagation path from shadowing, fading and multi-path phenomenon. The Time Tracking Loop samples and adjusts the received signal by means of summing and scaling, to provide an additional random bit. Because the propagation path delay varies randomly, one skilled in the art will understand that the random variable may be extracted at an arbitrary rate from the Time Tracking Loop. Moreover, more or less than one bit may be extracted in the random number generator. [0018] Through novel use of the Receive AGC circuit, In Phase/Quadrature (I/Q) DC Offset Correction Loop, and Time Tracking Loop, the exemplary embodiment of the present invention produces 4 bits of random data per frame interval during phone use. Because the data is generated with hardware, it is truly random, rather than software generated data, which must be pseudo-random by nature. Such sequences of pseudo-random data are highly susceptible to being deciphered by a third party, while random data produced by the present invention is not. [0019] FIG. 2 illustrates a simplified partial signal path within common CDMA phone receive hardware apparatus. FIG. 2 shows the path of the signal only through the hardware used by the invention to generate random data. [0020] Antenna 202 is a transducer that converts RF (radio-frequency) fields into (alternating current) AC or vice-versa. A receive antenna intercepts RF energy and delivers AC to electronic equipment. The received analog signal reaches antenna element 202, and is downconverted to a baseband analog signal by the receive demodulator element 204. After downconversion, the signal passes to an Analog to Digital Converter element 206. Continue reading... Full patent description for Random number generation for encrypting cellular communications Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Random number generation for encrypting cellular communications patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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