Abstract:
In a device having a data channel, in which random numbers are needed, such as a data storage device that uses random numbers to generate keys for cryptographic applications, random numbers are generated by a deterministic random bit generator seeded by bits derived from noise on the channel itself. The bits may be extracted from the least significant bits of the data signal after it is digitized, because those bits correspond to the noise in the signal. The extraction may occur immediately after digitization, or after subsequent filtering. A data signal emulator may be provided to simulate a data signal if a seed is required at a time when there is no data activity on the channel. The extracted bits may be post-processed to remove bias before the seed is provided to the deterministic random bit generator.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This claims the benefit of U.S. Provisional Patent Application No. 60/882,058, filed Dec. 27, 2006, the contents of which are hereby incorporated by reference herein in their entirety. 
    
    
     BACKGROUND 
     This disclosure relates to an entropy source for the generation of random numbers, and more particularly for seeding a random number generator. 
     Random number generation techniques are well-known. Most commonly, random numbers or bits are generated by providing a “pseudorandom” number or bit generator which generates numbers or bits in a deterministic way (such a pseudorandom number generator may be referred to as a “deterministic random number, or bit, generator”) but accepts an input, known as a “seed,” that causes the output to differ. Thus, in very early and primitive “random” number generators, the deterministic random number generator may have been a memory preprogrammed with a large number of “random” entries, which output the next one of those entries each time it was called, starting from the first entry each time it was powered up. This very simple list of numbers could be seeded by multiplying the output by the time of day, taken from the system clock. For primitive applications, this may have been sufficient. 
     More sophisticated deterministic random bit generators (DRBGs) may rely on an algorithm rather than a list, but are equally predictable once the seed is known. Thus, the randomness of the output depends on the randomness of the seed. 
     One common use for random numbers is in key generation for data security operations such as encryption/decryption and authentication. Such operations are becoming increasingly common in data storage devices. In data storage devices, short access times are important. Therefore, little time is available for generating random numbers without affecting data throughput, and yet, while current technology does not allow the generation of truly random numbers, the random numbers, and therefore the seeds, should be as close as possible to random for maximum security. Henceforth, these will be referred to as “reliably” random numbers. 
     SUMMARY 
     In accordance with embodiments of the present invention, reliably random numbers are generated by a relatively fast deterministic random bit generator, seeded by an entropy source generator based on a non-deterministic physical phenomenon in the device for which the random numbers are being generated. Although the DRBG is required to be relatively fast, the entropy source generator need not be as fast, because the DRBG typically will not require frequent reseeding. Indeed, depending on the nature of the DRBG, the DRBG may need to be seeded so infrequently as to require, at one extreme, seeding only once during the lifetime of the device, unless the reseeding is initiated early because of, e.g., security concerns. 
     Any type of known DRBG may be used. For example, a DRBG can be implemented with components that are already present in the device, as discussed in more detail below. However, other arrangements also are possible, and the type of known DRBG may be dictated by the use or purpose for which the random numbers or bits are required. For example, for cryptographic applications, the DRBG in some embodiments may comply with a known standard, such as National Institute of Standards and Technology (NIST) Special Publication 800-90, or Federal Information Processing Standard (FIPS) Publication 140-2. Adherence to standards may also assure that the random numbers are as reliably random as they need to be. 
     In accordance with the invention, the entropy source generator relies on a natural source of entropy to generate random bits to seed the DRBG. Any fluctuating natural phenomenon can be used. Preferably, the phenomenon is one whose effects are inherently available in the device, rather than one that requires special hardware to detect. For example, thermal/temperature fluctuations can be used. 
     In a data storage device incorporating the invention, noise in the data channel itself can be used. In one embodiment, during a read event, after the data read from the storage device are digitized, bits representing noise are extracted from the data. Specifically, because the noise is more likely to reside in the lower range of the signal rather than the upper bits (if it were otherwise, the noise would overwhelm the data), the least significant bits are sampled for use in deriving a seed. These bits may be used directly, or may be further processed—e.g., to remove any bias that may exist in the entropy source—and then used to seed the DRBG. As an alternative, if a seed is needed when a read operation is not being performed and is not about to be performed, a “loop-back” mode can be used in which a read signal is emulated. Although in that case the noise will derive only from channel noise rather than from a combination of media noise and channel noise, the randomness of the noise would be sufficient. 
     In another embodiment, where not many random numbers are needed, the bits derived from the entropy source—either directly or after post-processing—may be used as the random numbers themselves, without using a DRBG. 
     In the case of a hard disk drive controller, after the data are read and sampled, they are digitized and filtered through a number of components. In accordance with the invention, the least significant bits—i.e., “the noise bits”—may be sampled at any point after the data are digitized. The noise bits may be sampled immediately after digitization—i.e., after the analog-to-digital converter. However, they can be sampled anywhere else in the channel, because filtering will not increase the random nature of the noise bits. 
     Therefore, in accordance with embodiments of the present invention, there is provided a method for generating random numbers for use with a device having a data channel subject to noise. The method includes generating reliably random seeds from the noise, and using those reliably random seeds to seed a deterministic random bit generator. A random number generator operating in accordance with the method also is provided. 
     An embodiment of a random number generator may comprise means for generating reliably random seeds from a data channel subject to noise, and means for using said reliably random seeds to seed a deterministic random bit generator. 
     The random number generator of this embodiment may further comprise means for post-processing said extracted bits to remove bias therefrom. 
     The random number generator of this embodiment may further comprise means for reading a source of analog data, and means for converting said analog data to a digital signal, wherein said means for generating extracts bits from said digital signal after conversion. The random number generator of this embodiment may further comprise means for filtering said digital signal, wherein said means for generating extracts said bits after said conversion and before said filtering. The random number generator of this embodiment may further comprise means for filtering said digital signal, wherein said means for generating extracts said bits after at least a portion of said filtering. That means for generating may extract said bits after said filtering. 
     The random number generator of this embodiment may further comprise means for emulating a data signal to generate entropy bits when there is no active data signal on said data channel. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other advantages of embodiments of the invention will be apparent upon consideration of the following detailed description, taken in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout, and in which: 
         FIG. 1  is a schematic representation of a generic random number generator; 
         FIG. 2  is a schematic representation of a seed generator for use in the random number generator of  FIG. 1 ; 
         FIG. 3  is a schematic representation of the seed generator of  FIG. 2  showing one embodiment of a post-processor; 
         FIG. 4  is a schematic diagram showing generation and buffering of entropy bits into memory for use in seed generation; 
         FIG. 5  is a schematic diagram showing how entropy bits may be sampled from a read data channel; 
         FIG. 6  is a schematic diagram of a read data channel showing where entropy bits may be sampled; 
         FIG. 7  is a block diagram of an exemplary hard disk drive that can employ the disclosed technology; and 
         FIG. 8  is a block diagram of an exemplary digital versatile disk drive that can employ the disclosed technology; 
         FIG. 9  is a block diagram of an exemplary high definition television that can employ the disclosed technology; 
         FIG. 10  is a block diagram of an exemplary vehicle that can employ the disclosed technology; 
         FIG. 11  is a block diagram of an exemplary cellular telephone that can employ the disclosed technology; 
         FIG. 12  is a block diagram of an exemplary set top box that can employ the disclosed technology; 
         FIG. 13  is a block diagram of an exemplary media player that can employ the disclosed technology; and 
         FIG. 14  is a block diagram of an exemplary solid state drive system that can employ the disclosed technology. 
     
    
    
     DETAILED DESCRIPTION 
     embodiments of the invention will now be described with reference to  FIGS. 1-6 . 
       FIG. 1  shows the general structure of a generic random number generator (RNG)  10 , including a seed generator  11  and a DRBG  12 . As can be seen, DRBG  12 , and hence RNG  10 , provides random number as an output  13  upon receipt of an external request  14 . DRBG  12  bases output  13  on an inputted seed  15  output by seed generator  11 , usually in response to request  16  from DRBG  12 . Although DRBG  12  itself is deterministic, as its name implies, RNG  10  as a whole can be considered nondeterministic (i.e., random) if seed generator  11  is good enough (i.e., random enough). 
     In a disk drive embodiment, random numbers may be used to establish and/or authenticate a secure connection, for key generation, etc. These operations do not directly affect data throughput. Therefore, while RNG  10  may be implemented in hardware, there would not be any significant performance penalty if it were implemented in firmware. 
     DRBG  12  should provide random numbers on demand. Several possible DRBGs are recommended by the National Institute of Standards and Technology in the aforementioned Special Publication 800-90, including Hash DRBG, HMAC DRBG (Key-Hashed Message Authentication Code DRBG), and CTR DRBG (Counter Mode DRBG). In an exemplary disk drive embodiment, DRBG  12  may be a CTR DRBG based on an AES-128 (Advanced Encryption Standard 128). 
     On the other hand, seed generator  11  can operate slowly, because seeds are not needed often. For example, a CTR-DRBG-based DRBG may need a new seed only after 2 48  calls. Even at one call per second in continuous operation, a new seed would not be needed for 2 48  seconds ≈2.8×10 14  seconds or approximately 8.9 million years. Even if one million calls were made every second, a new seed would be needed only every few years. Thus, seed generator  11  could operate relatively slowly, especially if DRBG  12  requests a seed in advance after receiving a certain number of calls for random numbers prior to its limit being reached. Even if a seed is needed unexpectedly, such as in the case of user request because of concern that the security of the current seed has been compromised, a delay in responding to such requests would not affect data throughput. The effect of a slow seed generator  11  could be further mitigated by generating a succession of seeds in advance as long as they can be stored securely. A new seed would then be available instantly upon request. 
       FIG. 2  shows an exemplary seed generator  11  containing an entropy source  21  and a post-processor  22 . Entropy source  21  may be based on any substantially truly random physical phenomenon (as discussed both above and below), but in general should satisfy several desirable properties. First, the entropy bits should be independent and uncorrelated. Second, entropy source  21  should be secure, meaning that one should not be able to predict the next bit of entropy based on the previous observations, nor should one be able to deduce past bits based on present observations, so that if someone were to learn certain bits, neither past nor future seeds could be determined. Finally, entropy source  21  should be unbiased, meaning that the probability of occurrence of a “1” equals to probability of occurrence of a “0”. 
     The latter property is not easy to achieve in practice. Therefore, post-processor  22  may be provided. Post-processor  22  may apply any well-known technique to remove any bias that may exist in entropy source  21 . For example, for a Bernoulli random variable X, the bias b x  may be defined as the measure of how close X is to being a “fair coin”:
 
 b   x   =|P ( X= 1)−½|=| P ( X= 0)−½|
 
Note that b is between 0 and ½, with b=0 being the value for a “fair coin,” and b=0.5 being the value for a constant random variable (i.e., one with no randomness at all).
 
     Therefore, if {X i } is a sequence of independent Bernoulli random variables with probability of success {p i }, where the p i &#39;s are between 0 and 1, and X is the binary exclusive-OR of the X i &#39;s, then the bias of X is given by 
     
       
         
           
             
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     This suggests that one way to remove the bias from an entropy source is to exclusive-OR a number of random bits together. This effectively is a form of downsampling of the entropy bits, which is acceptable because many more bits are generated than actually may be needed. 
     For example, if the entropy source produces a stream of independent Bernoulli random variables having probability of success equals to 0.75, then the bias for X i  is 0.25, the bias of X is equal to 0.5×(2×0.25) n =0.5×0.5 n . If 15 variables are XORed, then n=15 and the bias is approximately 1.5×10 −5 , which is negligible. 
     Therefore, one implementation of post-processor  22  is linear feedback shift register  31  of  FIG. 3 , which corresponds to an irreducible polynomial. This guarantees a long period before the output bits start repeating. This circuit also satisfies the foregoing requirement that the output be an exclusive-OR of the input bits. 
     Returning to entropy source  21 , it may be any physical phenomenon that can be measured on the device, including temperature or thermal fluctuations, etc. In accordance with the invention, in the case of the read data channel of a data storage device, inherent channel noise, which may include as components both media noise, introduced in the reading of data from the disk surface, and electronic noise introduced subsequently, although media noise is the dominant component. 
     As stated above, channel noise manifests itself in the least significant bits—if it were otherwise, the noise would overwhelm the data—e.g., of the output signals of ADC 54  or FIR filter  56  (see  FIG. 5 ). Therefore, in one embodiment the least significant bits are sampled as the entropy bits. However, if the underlying transmitted bits are too regular, the noise may not be sufficiently random (e.g., if the noise is primarily data dependent—i.e., is a strong function of the written bits—then if the underlying data pattern is periodic, such as 11001100 . . . , the noise may be periodic as well). For example, in some embodiments the signals may not be sampled during the repetitious preamble and postamble patterns in the data, but only after a sync-byte detect signal indicates that actual data have been detected. Similarly, in some embodiments the signals may not be sampled during a thermal asperity event or other detected defect, when the signals may either be constant or toggling in a regular pattern. 
     The number of bits required is not great and therefore the data may be downsampled (as by exclusive-ORing as described above) to as little as one bit per channel symbol. The signals from which the random noise bits are extracted may not be the transmitted data themselves. Instead the random noise bits may be extracted from signals obtained during the signal processing that is performed on the received waveform in order to recover the transmitted data bits. Some of these signals may be digital and some may be analog. Some may arrive at the baud rate—one for every transmitted bit, while others may be oversampled—multiple samples per one transmitted bit. Some signals—such as, the aforementioned FIR and ADC outputs—may arrive as one sample per transmitted bit. Because throughput is not an issue, instead of grabbing every ADC output, one might opt to sample only every 10th ADC output (i.e., one bit per symbol), essentially trading throughput for complexity. Further down-sampling may occur during the post-processing stage. As shown in  FIG. 4 , the entropy bits  41  derived from the channel may be buffered in to a memory (e.g., RAM)  42  that is accessible by the firmware (or hardware)  43  in which seed generator  20  is implemented. 
     The size of the RAM  42  preferably may be determined by the down-sampling rate of the entropy source, and by the rate at which the bits, once buffered, can be further processed. This will be implementation dependent. 
     An additional counter  44  (NUM_RECEIVED_ENTROPY_BITS), may be provided to keep track of number of entropy bits received from the channel, to determine when the requested number of bits has been reached. The ENTROPY_SOURCE_VALID signal may be used to disable both RAM  42  and counter  44 —e.g., during a thermal asperity event or other detected defect, as discussed above. 
       FIG. 5  shows how entropy bits may be sampled from a read data channel  50 . Analog data signal  52  is read from media  51  and processed through analog front end (AFE)  53 , which may include low-pass filtering, gain control, etc. The filtered signal is then digitized in analog-to-digital converter (ADC)  54 . The digitized data  55  are passed to finite impulse response (FIR) filter  56  for equalization and filtering, and filtered data  57  are passed Viterbi detector  58  for decoding. 
     In accordance with an embodiment of the present invention, the least significant bits of digitized data  55  are also used as a source of entropy bits. As stated above, any noise in the signal would tend to cluster in the least significant bits; if it were present in more significant bits, the “noise” would overwhelm the signal. In the embodiment shown, data  55  include six bits  500  (5:0), which may be downsampled at  501  to one bit, as shown. 
     In cases where a seed is required but no data are being read, it is possible to perform a read of some predetermined portion of media  51 . However, rather than spin the disk unnecessarily, a signal emulator  59  may be provided to generate a data stream from which entropy bits can be derived in cases where no data are being read. The continuous waveform provided to the channel detector by emulator  59  may be noise free. However, electronic noise will be picked up in the course of processing the signal. That noise will then be captured by the entropy generator. Alternatively, if, as discussed above, a seed is sought before the maximum number of random numbers has been generated from the previous seed, it should almost always be possible to wait for the next read operation to derive the next seed. 
       FIG. 6  shows a more complete read data channel  60 , but without the entropy bit derivation components  500 - 502 . Channel  60  includes media  51 , analog front end (AFE)  53 , analog-to-digital converter (ADC)  54 , finite impulse response (FIR) filter  56 , and Viterbi detector  58  as in  FIG. 5 . Channel  60  also includes channel reconstructive filter  61 , as well as loops  62  that are responsible for acquiring timing, gains, and also adapting FIR filter taps. Although in  FIG. 5 , the entropy bits are tapped at point  63  directly after digitization at ADC  54 , in fact they also can be tapped at least at point  64  after channel reconstructive filter  61  or point  65  within loops  62 . Although the noise present at point  63  may be filtered in FIR filter  56  and channel reconstructive filter  61 , and the “shape” of the noise will be different, the random nature of the noise is not changed by filtering. Therefore, the noise can be tapped for entropy bits essentially anywhere after digitization. 
     Thus it is seen that random numbers in a data storage device can be generated quickly using a DRBG with an entropy source based on characteristics of the device itself to provide a ready source of seeds for the DRBG without adding additional hardware. 
     Referring now to  FIGS. 7-14 , exemplary implementations of the present invention are shown. 
     Referring now to  FIG. 7 , an embodiment of the present invention can be implemented in a hard disk drive  600 . This embodiment of the present invention may implement either or both signal processing and/or control circuits, which are generally identified in  FIG. 7  at  602 . In some implementations, the signal processing and/or control circuit  602  and/or other circuits (not shown) in the HDD  600  may process data, perform coding and/or encryption, perform calculations, and/or format data that is output to and/or received from a magnetic storage medium  606 . 
     The HDD  600  may communicate with a host device (not shown) such as a computer, mobile computing devices such as personal digital assistants, cellular telephones, media or MP3 players and the like, and/or other devices, via one or more wired or wireless communication links  608 . The HDD  600  may be connected to memory  609  such as random access memory (RAM), low latency nonvolatile memory such as flash memory, read only memory (ROM) and/or other suitable electronic data storage. 
     Referring now to  FIG. 8 , an embodiment of the present invention can be implemented in a digital versatile disk (DVD) drive  700 . This embodiment of the present invention may implement either or both signal processing and/or control circuits, which are generally identified in  FIG. 8  at  702 , and/or mass data storage of the DVD drive  700 . The signal processing and/or control circuit  702  and/or other circuits (not shown) in the DVD drive  700  may process data, perform coding and/or encryption, perform calculations, and/or format data that is read from and/or data written to an optical storage medium  706 . In some implementations, the signal processing and/or control circuit  702  and/or other circuits (not shown) in the DVD drive  700  can also perform other functions such as encoding and/or decoding and/or any other signal processing functions associated with a DVD drive. 
     DVD drive  700  may communicate with an output device (not shown) such as a computer, television or other device, via one or more wired or wireless communication links  707 . The DVD drive  700  may communicate with mass data storage  708  that stores data in a nonvolatile manner. The mass data storage  708  may include a hard disk drive (HDD). The HDD may have the configuration shown in  FIG. 7  The HDD may be a mini-HDD that includes one or more platters having a diameter that is smaller than approximately 1.8″. The DVD drive  700  may be connected to memory  709  such as RAM, ROM, low-latency nonvolatile memory such as flash memory, and/or other suitable electronic data storage. 
     Referring now to  FIG. 9 , an embodiment of the present invention can be implemented in a high definition television (HDTV)  800 . This embodiment of the present invention may implement either or both signal processing and/or control circuits, which are generally identified in  FIG. 9  at  822 , a WLAN interface and/or mass data storage of the HDTV  800 . The HDTV  800  receives HDTV input signals in either a wired or wireless format and generates HDTV output signals for a display  826 . In some implementations, signal processing circuit and/or control circuit  822  and/or other circuits (not shown) of the HDTV  800  may process data, perform coding and/or encryption, perform calculations, format data and/or perform any other type of HDTV processing that may be required. 
     The HDTV  800  may communicate with mass data storage  827  that stores data in a nonvolatile manner such as optical and/or magnetic storage devices. At least one HDD may have the configuration shown in  FIG. 7  and/or at least one DVD drive may have the configuration shown in  FIG. 8 . The HDD may be a mini-HDD that includes one or more platters having a diameter that is smaller than approximately 1.8″. The HDTV  800  may be connected to memory  828  such as RAM, ROM, low-latency nonvolatile memory such as flash memory, and/or other suitable electronic data storage. The HDTV  800  also may support connections with a WLAN via a WLAN network interface  829 . 
     Referring now to  FIG. 10 , an embodiment of the present invention implements a control system of a vehicle  900 , a WLAN interface and/or mass data storage of the vehicle control system. In some implementations, this embodiment of the present invention may implement a powertrain control system  932  that receives inputs from one or more sensors such as temperature sensors, pressure sensors, rotational sensors, airflow sensors and/or any other suitable sensors and/or that generates one or more output control signals such as engine operating parameters, transmission operating parameters, and/or other control signals. 
     Embodiments of the present invention may also be implemented in other control systems  940  of the vehicle  900 . The control system  940  may likewise receive signals from input sensors  942  and/or output control signals to one or more output devices  944 . In some implementations, the control system  940  may be part of an anti-lock braking system (ABS), a navigation system, a telematics system, a vehicle telematics system, a lane departure system, an adaptive cruise control system, a vehicle entertainment system such as a stereo, DVD, compact disc and the like. Still other implementations are contemplated. 
     The powertrain control system  932  may communicate with mass data storage  946  that stores data in a nonvolatile manner. The mass data storage  946  may include optical and/or magnetic storage devices for example hard disk drives HDD and/or DVDs. At least one HDD may have the configuration shown in  FIG. 7  and/or at least one DVD drive may have the configuration shown in  FIG. 8 . The HDD may be a mini-HDD that includes one or more platters having a diameter that is smaller than approximately 1.8″. The powertrain control system  932  may be connected to memory  947  such as RAM, ROM, low latency nonvolatile memory such as flash memory, and/or other suitable electronic data storage. The powertrain control system  932  also may support connections with a WLAN via a WLAN network interface  948 . The control system  940  may also include mass data storage, memory and/or a WLAN interface (none shown). 
     Referring now to  FIG. 11 , an embodiment of the present invention can be implemented in a cellular telephone  1000  that may include a cellular antenna  1051 . This embodiment of the present invention may implement either or both signal processing and/or control circuits, which are generally identified in  FIG. 11  at  1052 , a WLAN interface and/or mass data storage of the cellular phone  1000 . In some implementations, the cellular telephone  1000  includes a microphone  1056 , an audio output  1058  such as a speaker and/or audio output jack, a display  1060  and/or an input device  1062  such as a keypad, pointing device, voice actuation and/or other input device. The signal processing and/or control circuits  1052  and/or other circuits (not shown) in the cellular telephone  1000  may process data, perform coding and/or encryption, perform calculations, format data and/or perform other cellular telephone functions. 
     The cellular telephone  1000  may communicate with mass data storage  1064  that stores data in a nonvolatile manner such as optical and/or magnetic storage devices—for example hard disk drives (HDDs) and/or DVDs. At least one HDD may have the configuration shown in  FIG. 7  and/or at least one DVD drive may have the configuration shown in  FIG. 8 . The HDD may be a mini-HDD that includes one or more platters having a diameter that is smaller than approximately 1.8″. The cellular telephone  1000  may be connected to memory  1066  such as RAM, ROM, low-latency nonvolatile memory such as flash memory, and/or other suitable electronic data storage. The cellular telephone  1000  also may support connections with a WLAN via a WLAN network interface  1068 . 
     Referring now to  FIG. 12 , an embodiment of the present invention can be implemented in a set top box  1100 . This embodiment of the present invention may implement either or both signal processing and/or control circuits, which are generally identified in  FIG. 12  at  1184 , a WLAN interface and/or mass data storage of the set top box  1100 . Set top box  1100  receives signals from a source  1182  such as a broadband source and outputs standard and/or high definition audio/video signals suitable for a display  1188  such as a television and/or monitor and/or other video and/or audio output devices. The signal processing and/or control circuits  1184  and/or other circuits (not shown) of the set top box  1100  may process data, perform coding and/or encryption, perform calculations, format data and/or perform any other set top box function. 
     Set top box  1100  may communicate with mass data storage  1190  that stores data in a nonvolatile manner. The mass data storage  1190  may include optical and/or magnetic storage devices for example hard disk drives HDD and/or DVDs. At least one HDD may have the configuration shown in  FIG. 7  and/or at least one DVD drive may have the configuration shown in  FIG. 8 . The HDD may be a mini-HDD that includes one or more platters having a diameter that is smaller than approximately 1.8″. Set top box  1100  may be connected to memory  1194  such as RAM, ROM, low-latency nonvolatile memory such as flash memory, and/or other suitable electronic data storage. Set top box  1100  also may support connections with a WLAN via a WLAN network interface  1196 . 
     Referring now to  FIG. 13 , an embodiment of the present invention can be implemented in a media player  1200 . This embodiment of the present invention may implement either or both signal processing and/or control circuits, which are generally identified in  FIG. 13  at  1204 , a WLAN interface and/or mass data storage of the media player  1200 . In some implementations, the media player  1200  includes a display  1207  and/or a user input  1208  such as a keypad, touchpad and the like. In some implementations, the media player  1200  may employ a graphical user interface (GUI) that typically employs menus, drop down menus, icons and/or a point-and-click interface via the display  1207  and/or user input  1208 . Media player  1200  further includes an audio output  1209  such as a speaker and/or audio output jack. The signal processing and/or control circuits  1204  and/or other circuits (not shown) of media player  1200  may process data, perform coding and/or encryption, perform calculations, format data and/or perform any other media player function. 
     Media player  1200  may communicate with mass data storage  1210  that stores data such as compressed audio and/or video content in a nonvolatile manner. In some implementations, the compressed audio files include files that are compliant with MP3 format or other suitable compressed audio and/or video formats. The mass data storage may include optical and/or magnetic storage devices for example hard disk drives HDD and/or DVDs. At least one HDD may have the configuration shown in  FIG. 7  and/or at least one DVD drive may have the configuration shown in  FIG. 8 . The HDD may be a mini-HDD that includes one or more platters having a diameter that is smaller than approximately 1.8″. Media player  1200  may be connected to memory  1214  such as RAM, ROM, low-latency nonvolatile memory such as flash memory, and/or other suitable electronic data storage. Media player  1200  also may support connections with a WLAN via a WLAN network interface  1216 . Still other implementations in addition to those described above are contemplated. 
     Referring now to  FIG. 14 , an embodiment of the present invention can be implemented in a solid-state drive  1300 . This embodiment of the present invention may include flash memory cells  1301  or other low-latency nonvolatile memory, and/or other suitable electronic data storage. In some implementations, a flash controller  1302 , which may function as an interface to flash memory cells  1301 , and/or other circuits (not shown) in the solid-state drive  1300  may process data, perform coding and/or encryption, perform calculations, and/or format data that is output to and/or received from flash memory cells  1301 . Still other implementations in addition to those described above are contemplated. 
     It will be understood that the foregoing is only illustrative of the principles of the invention, and that the invention can be practiced by other than the described embodiments, which are presented for purposes of illustration and not of limitation, and the present invention is limited only by the claims which follow.