An analysis system that is able to obtain correct encryption key is provided. The analysis system includes a processing circuitry configured to function as a cryptanalysis processing unit. The cryptanalysis processing unit includes: a key candidate extraction unit that is configured to extract, from second data, one or more candidates of key data that include an encryption key that enables to decrypt first data encrypted by a specific encryption scheme, based on data indicating a feature of the key data; and a decryption unit that is configured to extract, from the extracted candidates of key data, correct key data that enables to correctly decrypt the encrypted first data, based on a result of decrypting the first data by use of the extracted candidates of key data.