A cryptographic communication apparatus, comprising: an encryption part adapted to prefetch an encryption key for encrypting plaintext data before receiving the plaintext data and, when receiving the plaintext data, encrypt the plaintext data using the encryption key; a decryption part adapted to prefetch a decryption key for decrypting cipher text data before receiving the cipher text data and, when receiving the cipher text data, decrypt the cipher text data using the decryption key; and a control unit adapted to control a volume of the encryption key to be prefetched and a volume of the decryption key to be prefetched, wherein the control unit is adapted to allocate a common key shared with a communication destination apparatus, to the encryption key or the decryption key and increase the volume of the encryption key to be prefetched and the volume of the decryption key to be prefetched with an increase in speeds at which the common key is generated, increase the volume of the encryption key to be prefetched with an increase in a residual volume of an encryption key holding part holding the encryption key allocated from the common key, and increase the volume of the decryption key to be prefetched with an increase in a residual volume of a decryption key holding part holding the decryption key allocated from the common key, and the control unit is adapted to: identify a volume of communication traffic, a volume of transmission traffic, and a volume of reception traffic by using at least either one of communication statistical information and communication history information of cryptographic communication by the cryptographic communication apparatus; and increase the volume of the encryption key to be prefetched and the volume of the decryption key to be prefetched with an increase in the volume of the communication traffic; and increase the volume of the encryption key to be prefetched and decrease the volume of the decryption key to be prefetched when the volume of the transmission traffic is greater than the volume of the reception traffic. an encryption part adapted to prefetch an encryption key for encrypting plaintext data before receiving the plaintext data and, when receiving the plaintext data, encrypt the plaintext data using the encryption key; a decryption part adapted to prefetch a decryption key for decrypting cipher text data before receiving the cipher text data and, when receiving the cipher text data, decrypt the cipher text data using the decryption key; and a control unit adapted to control a volume of the encryption key to be prefetched and a volume of the decryption key to be prefetched, wherein the control unit is adapted to allocate a common key shared with a communication destination apparatus, to the encryption key or the decryption key and increase the volume of the encryption key to be prefetched and the volume of the decryption key to be prefetched with an increase in speeds at which the common key is generated, increase the volume of the encryption key to be prefetched with an increase in a residual volume of an encryption key holding part holding the encryption key allocated from the common key, and increase the volume of the decryption key to be prefetched with an increase in a residual volume of a decryption key holding part holding the decryption key allocated from the common key, and the control unit is adapted to: identify a volume of communication traffic, a volume of transmission traffic, and a volume of reception traffic by using at least either one of communication statistical information and communication history information of cryptographic communication by the cryptographic communication apparatus; and increase the volume of the encryption key to be prefetched and the volume of the decryption key to be prefetched with an increase in the volume of the communication traffic; and increase the volume of the encryption key to be prefetched and decrease the volume of the decryption key to be prefetched when the volume of the transmission traffic is greater than the volume of the reception traffic. identify a volume of communication traffic, a volume of transmission traffic, and a volume of reception traffic by using at least either one of communication statistical information and communication history information of cryptographic communication by the cryptographic communication apparatus; and increase the volume of the encryption key to be prefetched and the volume of the decryption key to be prefetched with an increase in the volume of the communication traffic; and increase the volume of the encryption key to be prefetched and decrease the volume of the decryption key to be prefetched when the volume of the transmission traffic is greater than the volume of the reception traffic.