Computer program product and method for processing information to obtain an HMAC

One embodiment is a computer program product for processing information to obtain an HMAC, comprising: by using a padding circuit, generating first key data by adding 0 with respect to secret key data, setting the secret key data as second key data, or generating third key data by adding 0 with respect to a first digest value, according to comparison result of a second key length and a block length of the hash function, and performing an exclusive OR operation with a second constant with respect to one of the first key data, the second key data, and the third key data to calculate first data; by using a hash calculation circuit, obtaining the first digest value, and obtaining a second digest value, by using a holding circuit, storing the secret key data or the first digest value; and by using a control unit, managing a processing state for calculating the HMAC.