1. A cryptographic processing method comprising: generating a third encrypted polynomial that corresponds to a result of encrypting a third polynomial by a computer, by use of a result of multiplying a first encrypted polynomial obtained by encrypting a first polynomial that corresponds to a first vector by a second encrypted polynomial obtained by encrypting a second polynomial that corresponds to a second vector, the third polynomial including a first term that has a coefficient based on an inner product of the first vector and the second vector and a second term other than the first term, wherein the computer masks a coefficient of the second term by performing cryptographic masking on the result of multiplying the first encrypted polynomial by the second encrypted polynomial; and outputting cryptographic information that represents the third encrypted polynomial.