Patent Application: US-201313866257-A

Abstract:
a method and apparatus is provided for the operation of a secure and deduplicated write once read many virtual disk which exceeds the write performance of traditional cryptographic methods . this is achieved through the utilization of a time - memory tradeoff via the empty space on a virtual disk at format time . traditionally empty space is zeroed to indicate that data is not present . when implementing the apparatus , the empty space is filled with the output of a symmetric - key algorithm uniquely keyed for that specific disk . from an information theoretic point of view , the format operation stores cryptographically structured data , rather than purely redundant data , enabling the write operation that encodes data to be stored on the disk to operate without additional cryptographic computation . this reduced computation requirement for encoding enables the computation required deduplication to operate as if encoding was not being performed , resulting in a net throughput increase .

Description:
in order to illustrate the invention , we will treat a write once read many virtual disk as if it was a physical disk with worm properties just as many operating systems and hypervisors treat virtual disks as the representation of a physical disk that resides in main memory . we will divide the operation of the invention as a system into its corresponding format , write , and read methods or operations . we will also separate the encoding operation which is coupled with the write method , the decoding operation which is coupled with the read method , and deduplication and reduplication which are coupled with the write and read methods respectively . in order to illustrate the format method of the invention , we will use aes as an example symmetric - key algorithm , with a 256 - bit key and a 128 - bit block size , operating in counter mode ( ctr ) with a 96 - bit nonce and 32 - bit counter . the selection and use of aes - ctr in the following descriptions and examples is not meant to restrict the format method of the present invention in any manner . it should be known that the present invention can be implemented with any block cipher using a key or block size comprising any number of bits . also any reasonable scheme for generating and concatenating nonce and counter values comprising any number of bits can be used as long as each nonce and counter value concatenation is unique per block generated . for example , on a 64 - bit operating system it may be desirable to make the counter 64 - bits rather than 32 - bits . any mode of operation , such as aes - gcm if authenticated encryption is desired , can be used as long as that mode is capable of converting a block cipher into a stream cipher . for the specification of aes - gcm see [ 4 ]. all references to memory in the following descriptions of the preferred embodiments should be understood to imply a combination of processor cache and primary storage . we will define processor cache as memory which is located on the physical processor and primary storage as fast memory that is tightly coupled to the processor such as high - speed cache or random access memory ( ram ). it should be noted that secondary storage defined as slower memory that is more loosely coupled to the processor such as a solid state drive can also be considered primary storage in some cases . fig1 illustrates the format method of the invention where during the format operation processor cycles in a computing system are used in order to generate a keystream and write the keystream to a write once read many virtual disk . for the purpose of illustration we will present method using a single processor core for keystream generation with the understanding that multiple cores can be utilized to generate multiple partitions of the keystream in parallel . fig1 also illustrates the keying component of the format method in order to key the symmetric - key algorithm that is being utilized . generate key 101 uses a pseudorandom number generator ( prng ) 102 or random number generator ( rng ) 103 to generate key 105 for use with aes in format virtual disk 108 as illustrated by the pseudo code in table v . for best practices concerning pseudorandom number generation , see [ 3 ]. more specifically let k i = rng be the generation of a 256 - bit symmetric key using a cryptographically secure random or pseudorandom number generator . we can generate a key set composed of n 256 - bit keys k 1 , k 2 , . . . k n by sequentially calling the random or pseudorandom number generator . format virtual disk 108 uses key 105 provided by generate key 101 to key aes and operate produce key stream 104 of which is written sequentially to virtual disk 109 , using cycles from processor 106 as illustrated in table vi . more specifically , let m be defined as virtual disk 109 with a capacity of m 128 - bit blocks where a keystream of length j 128 - bit blocks will be stored . let m i = e k ( n ∥ i ) for i = 1 . . . j be defined as the 128 - bit value written to each memory location m i where e k is the encryption function of aes using a 256 - bit key k previously generated in generate key 101 , n is a 96 - bit psuedorandom nonce , and i is a 32 - bit counter incremented for the generation of each block with j & lt ;= m . the result of this computation is written to virtual disk 109 in the form of formatted block 110 . fig2 illustrates the write method according to an embodiment of the present invention . we will assume a target data 200 and a previously formatted virtual disk 201 are available in memory . each block of data is first deduplicated and then encoded using a corresponding block read from the virtual disk 201 that was generated according to the method outlined in fig1 . this process of deduplicating then encoding is illustrated in table vii . more specifically let d 1 , d 2 , . . . d n or d 202 represent target data 200 of n 128 - bit blocks that are deduplicated . let p 1 , p 2 , . . . p n or p 203 represent a plaintext , after the previous deduplication step , of n 128 - bit blocks and j be the number of 128 - bit blocks of virtual disk 201 available in memory . let the instructions executed for encoding each plaintext block p i be defined as c i = p i ⊕ m i , i & lt ;= j . let c 1 , c 2 , . . . c n or c 204 represent the resulting ciphertext of n 128 - bit blocks where m 203 is a preformatted block . even though fig2 illustrates the write method using the same size blocks for deduplication d 202 as well as encoding p 203 , it should be assumed that the block size for each operation is independent of each other . it should also be noted that each encoded block c 204 written to virtual disk 201 resides in the same location as the original block m 203 present from the format operation . in this manner no additional space is required for the operation as a whole . fig3 illustrates read method according to an embodiment of the present invention . we will assume a previously written virtual disk 301 is available in memory that was either transmitted to the reading computer via a network connection or presented via a storage controller on media that was in long term storage . each block of data in virtual disk 301 is decoded and reduplicated as illustrated in table viii . more specifically let the instructions executed for decoding each 128 - bit ciphertext block c i or c 304 be p i = e k ( n ∥ i )⊕ c i , where e k is the encryption function 305 for aes using a 256 - bit key k , n is a 96 - bit pseudorandom nonce , i is a 32 - bit counter incremented for the processing of each block , and n is the total number of 128 - bit blocks , with i & gt ; j . let d 1 , d 2 , . . . d n or d 302 represent resulting data 300 of n 128 - bit blocks that are reduplicated from blocks p 1 , p 2 , . . . p n or p 303 resulting from the decoding operation . for the read operation of the invention the computational rate of the symmetric - key algorithm will dictate the level of performance . for the details concerning the options for generating and concatenating counter and nonce values for a specific key see [ 2 ]. also note that only the encryption function of the symmetric - key algorithm is needed when operating in ctr or gcm mode . fig4 illustrates the method of using arbitrary parallelism while performing the format method according to an embodiment of the present invention . for the purpose of illustration we will define a logical processor as a thread of execution that is capable of performing instructions on a data stream independent of the logical or physical implementation of multiprocessing specific to that system . multiprocessor capability can be presented to the invention through multiple physical processors , processor cores , or a processor or operating system threading mechanism . the method of parallelization we will present is based on the simple structure of dividing virtual disk 409 into multiple sequential partitions and operating on those partitions in parallel . a virtual disk 409 is divided up into n partitions which each serve as input to n logical processors 406 . each logical processor 406 is responsible for formatting a partition of virtual disk 409 as illustrated in table ix . more specifically let v 1 , v 2 , . . . , v n be a set of n virtual disk 409 partitions . let l 1 , l 2 , . . . , l n represent n logical processors . each logical processor l k generates a corresponding partition of keystream using produce key stream 404 and writes it to virtual disk 409 partition v k . let m be defined as virtual disk 409 partition with a capacity of m 128 - bit blocks where a key stream 407 of length j 128 - bit blocks will be stored . let m i = e k ( n ∥ i ) for i = 1 . . . j be defined as the 128 - bit value written to each memory location m i where e k is the encryption function of aes using a 256 - bit key 405 generated as illustrated in fig1 generate key 101 , n is a 96 - bit psuedorandom nonce , and i is a 32 - bit counter incremented for the generation of each block with j & lt ;= m in the form of formatted block 410 . the degree of parallel operation the invention is able to create is defined by the number of logical processors available for generating the key stream used to format virtual disk 409 . the maximum theoretical speedup can be defined as i / n where i is the symmetric - key algorithm encoding rate and n is the number of logical processors . the actual speedup will depend on the architecture of the computing system executing the algorithm based on its ability to cache data from multiple memory streams and other hardware specific issues when executing parallel operations . it should be noted that when using the invention the actual encoding performed by the system is mathematically equivalent to encoding performed by a system that is not using the invention . therefore if data is written to the invention ( a write once read many storage system ) it can be read from the invention and decoded and reduplicated without the inventions read method since any device that has the equivalent symmetric - key algorithm and reduplication algorithm can read the data . while certain embodiments have been described above , other embodiments will be obvious in view of the above description to those skilled in the art . for example , the invention will work with any symmetric - key block cipher such as des or triple - des , in which a block cipher can be transformed into a stream cipher using certain modes of operation such as ctr ( counter ) mode , ofb ( output feedback ) mode , and cfb ( cipher feedback ) mode . it should be understood that the invention could be practiced with modification and alteration within the spirit and scope of the appended claims . the description above is not intended to be exhaustive or to limit the invention to the precise form disclosed . it should be understood that the invention can be practiced with modification and alteration and that the invention be limited only by the claims and the equivalents thereof . us2010 / 0235332 “ apparatus and method to deduplicate data ” haustein et al , 12 / 404 , 988 , mar . 16 , 2009 us7433472 “ digital content distribution system ”, ivan hugh mclean et al , oct . 7 , 2008 ep1732259 b1 “ method and system for securely storing and transmitting data by applying a one - 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