A decryption device comprising: a ciphertext acquisition unit adapted to acquire a ciphertext ct x in which a vector x is encrypted using encryption setting information of a size depending on a size of the vector x, the encryption setting information being defined using as input public information of a fixed size; a secret key acquisition unit adapted to acquire a secret key sk y in which a vector y is set using key setting information of a size depending on a size of the vector y, the key setting information being defined using as input the public information; and a decryption unit adapted to decrypt the ciphertext ct x acquired by the ciphertext acquisition unit with the secret key sk y acquired by the secret key acquisition unit to calculate an inner-product value of the vector x and the vector y; wherein the encryption setting information and the key setting information are defined by a pseudorandom function, using as input the public information; wherein the encryption setting information is a matrix B, wherein the ciphertext ct x includes an element [c i] i which is a group element in which a product of a target element x i and the matrix B is set, the target element x i being each element x i of the vector x, wherein the key setting information is an adjoint matrix B* of the matrix B, wherein the secret key sk y includes an element [k i] 2 which is a group element in which a product of a target element y i and the adjoint matrix B* is set, the target element y i being each element y i of the vector y, and wherein the decryption unit is adapted to calculate the inner-product value by calculating a pairing operation on the ciphertext ct x and the secret key sk y; wherein the ciphertext ct x includes an element [c i] i which is a group element in which an element c i indicated in Formula 1 is set, where an integer m is 1 or more and a matrix B i is the matrix B for each integer i of i = 1,..., m, and wherein the secret key sk y includes an element [k i] 2 which is a group element in which an element k i indicated in Formula 2 is set, where a set S is a set of integers and a matrix B ∗ i is the adjoint matrix B* for each integer i included in the set S c i: = x i 0 z 0 B i ∈ Z p 4 for i = 1,... m where x: = x 1,..., x m ∈ Z m, z ← U Z p k i: = y i 0 r i 0 B i ∗ ∈ Z p 4 for i ∈ S where y: = y i i ∈ S ∈ Z S, r i ← U Z p s.t. ∑ i ∈ S r i = 0 a ciphertext acquisition unit adapted to acquire a ciphertext ct x in which a vector x is encrypted using encryption setting information of a size depending on a size of the vector x, the encryption setting information being defined using as input public information of a fixed size; a secret key acquisition unit adapted to acquire a secret key sk y in which a vector y is set using key setting information of a size depending on a size of the vector y, the key setting information being defined using as input the public information; and a decryption unit adapted to decrypt the ciphertext ct x acquired by the ciphertext acquisition unit with the secret key sk y acquired by the secret key acquisition unit to calculate an inner-product value of the vector x and the vector y; wherein the encryption setting information and the key setting information are defined by a pseudorandom function, using as input the public information; wherein the encryption setting information is a matrix B, wherein the ciphertext ct x includes an element [c i] i which is a group element in which a product of a target element x i and the matrix B is set, the target element x i being each element x i of the vector x, wherein the key setting information is an adjoint matrix B* of the matrix B, wherein the secret key sk y includes an element [k i] 2 which is a group element in which a product of a target element y i and the adjoint matrix B* is set, the target element y i being each element y i of the vector y, and wherein the decryption unit is adapted to calculate the inner-product value by calculating a pairing operation on the ciphertext ct x and the secret key sk y; wherein the ciphertext ct x includes an element [c i] i which is a group element in which an element c i indicated in Formula 1 is set, where an integer m is 1 or more and a matrix B i is the matrix B for each integer i of i = 1,..., m, and wherein the secret key sk y includes an element [k i] 2 which is a group element in which an element k i indicated in Formula 2 is set, where a set S is a set of integers and a matrix B ∗ i is the adjoint matrix B* for each integer i included in the set S c i: = x i 0 z 0 B i ∈ Z p 4 for i = 1,... m where x: = x 1,..., x m ∈ Z m, z ← U Z p k i: = y i 0 r i 0 B i ∗ ∈ Z p 4 for i ∈ S where y: = y i i ∈ S ∈ Z S, r i ← U Z p s.t. ∑ i ∈ S r i = 0