SECURE COMPUTATION APPARATUS, SECURE COMPUTATION METHOD, AND PROGRAM
A secure computation apparatus includes a former half window frame column generation unit configured to generate, with respect to subVector ({g → }, s+1, i}, a bit column obtained by an OR operation performed on all bits from the end to each position as {w f→ }, a latter half window frame column generation unit configured to generate, with respect to subVector ({g → }, i+1, t}, a bit column obtained by an OR operation performed on all bits from the head to each position as {w l→ }, a window frame flag column generation unit configured to generate {w → } by combining {w f→ } and {w l→ }, an inverted window frame flag column generation unit configured to generate {w′ → } by performing a NOT operation on {w → }, a share conversion unit configured to convert {w′ → } into [[w′ → ]], and a product-sum operation unit configured to execute a product-sum operation on subVector ([[v′ → ]], s, t) and [[w′ → ]].
1 . A secure computation apparatus for performing arithmetic operations while keeping a database including a key column k → which is an attribute column and a data column v → which is a value column concealed, wherein
a group flag column g → represents a vector in which a value becomes 1 at a position where a value of the key column changes, and a value becomes 0 at other positions,
a share of a value x according to replicated secret sharing is represented as {x},
a share of the value x according to Shamir secret sharing is represented as ((x)),
a current row number is represented by i, a window frame start position is represented by s, and a window frame end position is represented by t,
the number of rows of the key column and the data column is set to 1, and the current row number i is incremented by one each time all flag column generation processing ends in a range of 0 or more and less than 1, the secure computation apparatus comprising:
processing circuitry configured to
generate, with respect to a vector subVector ({g → }, s+1, i} obtained by extracting elements from an (s+1)-th element to an i-th element of {g → }, a bit column obtained by an OR operation performed on all bits from the end to each position as a former half window frame flag column {w f→ };
generate, with respect to a vector subVector ({g → }, i+1, t) obtained by extracting elements from an (i+1)-th element to a t-th element of {g → , a bit column obtained by an OR operation performed on all bits from the head to each position as a latter half window frame flag column {w l→ };
generate a window frame flag column {w → } by combining the former half window frame flag column {w f→ } from the front side and the latter half window frame flag column {w l→ } from the rear side having (0) interposed between the former half window frame flag column {w f→ } and the latter half window frame flag column {w l→ };
generate an inverted window frame flag column {w′ → } by performing a NOT operation on the window frame flag column {w → };
convert the inverted window frame flag column {w′ → } into an inverted window frame flag column ((w′ → )); and
execute a product-sum operation on subVector ((v′ → )), s, t) obtained by extracting elements from s to t of a data column ((v′ → )) obtained by sorting a data column ((v → )) in ascending order and the inverted window frame flag column w′ → )).
2 . A secure computation method for performing arithmetic operations while keeping a database including a key column k → which is an attribute column and a data column v → which is a value column concealed, wherein
a group flag column g → represents a vector in which a value becomes 1 at a position where a value of the key column changes, and a value becomes 0 at other positions,
a share of a value x according to replicated secret sharing is represented as {x},
a share of the value x according to Shamir secret sharing is represented as ((x)),
a current row number is represented by i, a window frame start position is represented by s, and a window frame end position is represented by t,
the number of rows of the key column and the data column is set to 1, and the current row number i is incremented by one each time all flag column generation processing ends in a range of 0 or more and less than 1, the secure computation method comprising:
a step of generating, with respect to a vector subVector ({g → }, s+1, i} obtained by extracting elements from an (s+1)-th element to an i-th element of {g → }, a bit column obtained by an OR operation performed on all bits from the end to each position as a former half window frame flag column {w f→ };
a step of generating, with respect to a vector subVector ({g → }, i+1, t} obtained by extracting elements from an (i+1)-th element to a t-th element of {g → }, a bit column obtained by an OR operation performed on all bits from the head to each position as a latter half window frame flag column {w l→ };
a step of generating a window frame flag column {w → } by combining the former half window frame flag column {w f→ } from the front side and the latter half window frame flag column {w l→ } from the rear side having {0} interposed between the former half window frame flag column {w f→ } and the latter half window frame flag column (w l→ };
a step of generating an inverted window frame flag column {w′ → } by performing a NOT operation on the window frame flag column {w → };
a step of converting the inverted window frame flag column {w′ → } into an inverted window frame flag column ((w′ → ; and
a step of executing a product-sum operation on subVector ((v′ → , s, t) obtained by extracting elements from s to t of a data column ((v′ → )) obtained by sorting a data column ((v → )) in ascending order and the inverted window frame flag column][w′ → )).
3 . A non-transitory computer readable medium storing a computer program for causing a computer to function as the secure computation apparatus according to claim 1 .