Secure reading and writing apparatus, secure reading and writing method, and program
View Patent ↗Data is efficiently read from and written in a sequence without an access position being revealed. A secure reading and writing apparatus ( 1 ) receives a read command or a write command as input, and, when the read command is input, outputs a secret text [a[x]] which is an x-th element of a secret text sequence [a], and, when the write command is input, adds the secret text [a[x]] which is the x-th element of the secret text sequence [a], to a secret text [d]. A secure reading part ( 12 ) reads the secret text [a[x]] which is the x-th element from the secret text sequence [a]. A buffer addition part ( 13 ) adds a secret text [c] of an unreflected value c to the secret text [a[x]]. A buffer appending part ( 14 ) appends a secret text [x] and the secret text [d] to a write buffer [b]. When the number of elements of the write buffer [b] exceeds a predetermined value, a secure writing part ( 15 ) adds a value indicated with a secret text vector [b 1 ] to an access position of the secret text sequence [a] which is indicated with a secret text vector [b 0 ].
1. A secure reading and writing apparatus which receives a read command including a secret text sequence [a]=([a[0]], [a[1]], . . . , [a[n−1]]) having a size n and a secret text [x] of an access position x, or a write command including the secret text sequence [a], the secret text [x] and a secret text [d] of a value d to be written as input, and, when the read command is input, outputs a secret text [a[x]] which is an x-th element of the secret text sequence [a], and, when the write command is input, adds the secret text [d] to the secret text [a[x]] which is the x-th element of the secret text sequence [a],
the secure reading and writing apparatus comprising processing circuitry configured to:
store a write buffer [b]=([b 0 ], [b 1 ]) comprised of two secret text vectors [b 0 ] and [b 1 ];
when the write command is input, append the secret text [x] to the secret text vector [b 0 ], and append the secret text [d] to the secret text vector [b 1 ];
when the number of elements of the write buffer [b] exceeds a predetermined value, add a value indicated with the secret text vector [b 1 ] to an access position indicated with the secret text vector [b 0 ] among the secret text sequence [a];
when the read command is input, read the secret text [a[x]] which is the x-th element from the secret text sequence [a]; and
add a secret text [c] of an unreflected value c which is a sum of elements in which the access position indicated with the secret text vector [b 0 ] is equal to an access position indicated with the secret text [x] among elements of the secret text vector [b 1 ], to the secret text [a[x]] which is the x-th element of the secret text sequence [a].
2. The secure reading and writing apparatus according to claim 1 ,
wherein the processing circuitry computes the secret text [c] of the unreflected value c using the following formula:
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3. The secure reading and writing apparatus according to claim 1 ,
wherein the processing circuitry computes the secret text [c] of the unreflected value c using the following formula:
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4. The secure reading and writing apparatus according to claim 1 ,
wherein the secret text sequence [a], the secret text [x] and the secret text [d] are concealed through secret sharing in which, among shares obtained by dividing a plain text into s pieces, if arbitrary t shares are collected, the plain text can be reconstructed, while any information regarding the plain text cannot be obtained from less than t shares, where t is set as an integer equal to or greater than 1, and s≥2t−1;
the processing circuitry reads the secret text [a[x]] which is the x-th element from the secret text sequence [a] without the access position x being revealed; and
when the number of elements of the write buffer exceeds √n, the processing circuitry writes a value indicated with the secret text vector [b 1 ] to the access position indicated with the secret text vector [b 0 ] of the secret text sequence [a] without the access position x being revealed.
5. A secure reading and writing method to be executed by a secure reading and writing apparatus which receives a read command including a secret text sequence [a]=([a[0]], [a[1]], . . . , [a[n−1]]) having a size n and a secret text [x] of an access position x, or a write command including the secret text sequence [a], the secret text [x] and a secret text [d] of a value d to be written as input, and, when the read command is input, outputs a secret text [a[x]] which is an x-th element of the secret text sequence [a], and, when the write command is input, adds the secret text [d] to the secret text [a[x]] which is the x-th element of the secret text sequence [a],
the secure reading and writing method comprising performing by processing circuitry of the secure reading and writing apparatus:
storing a write buffer [b]=([b 0 ], [b 1 ]) comprised of two secret text vectors [b 0 ] and [b 1 ];
when the write command is input, appending the secret text [x] to the secret text vector [b 0 ], and appending the secret text [d] to the secret text vector [b 1 ];
when the number of elements of the write buffer [b] exceeds a predetermined value, adding a value indicated with the secret text vector [b 1 ] to an access position indicated with the secret text vector [b 0 ] among the secret text sequence [a];
when the read command is input, reading the secret text [a[x]] which is the x-th element from the secret text sequence [a]; and
adding a secret text [c] of an unreflected value c which is a sum of elements in which the access position indicated with the secret text vector [b 0 ] is equal to an access position indicated with the secret text [x] among elements of the secret text vector [b 1 ], to the secret text [a[x]] which is the x-th element of the secret text sequence [a].
6. A non-transitory computer readable medium having a program recorded thereon for causing a computer to function as a secure reading and writing apparatus which receives a read command including a secret text sequence [a]=([a[0]], [a[1]], . . . , [a[n−1]]) having a size n and a secret text [x] of an access position x, or a write command including the secret text sequence [a], the secret text [x] and a secret text [d] of a value d to be written as input, and, when the read command is input, outputs a secret text [a[x]] which is an x-th element of the secret text sequence [a], and, when the write command is input, adds the secret text [d] to the secret text [a[x]] which is the x-th element of the secret text sequence [a],
the secure reading and writing apparatus comprising processing circuitry configured to:
store a write buffer [b]=([b 0 ], [b 1 ]) comprised of two secret text vectors [b 0 ] and [b i ];
when the write command is input, append the secret text [x] to the secret text vector [b 0 ], and append the secret text [d] to the secret text vector [b i ];
when the number of elements of the write buffer [b] exceeds a predetermined value, add a value indicated with the secret text vector [b 1 ] to an access position indicated with the secret text vector [b 0 ] among the secret text sequence [a];
when the read command is input, read the secret text [a[x]] which is the x-th element from the secret text sequence [a]; and
add a secret text [c] of an unreflected value c which is a sum of elements in which the access position indicated with the secret text vector [b 0 ] is equal to an access position indicated with the secret text [x] among elements of the secret text vector [b 1 ], to the secret text [a[x]] which is the x-th element of the secret text sequence [a].