ENCRYPTION PROCESSING METHOD, SYSTEM AND INFORMATION PROCESSING APPARATUS

摘要

PROBLEM TO BE SOLVED: To re-encrypt plaintext of data to be concealed without exposing the plaintext.SOLUTION: An encryption processing method includes: processing for acquiring a first partial key 102 obtained from a private key 101 of a first user A; processing for generating second data by implementing decryption processing using the first partial key 102 on first data encrypted by a public key of the first user A and implementing mask processing by using a random number to mask the first data which are plaintext in accordance with an encryption system to be used; processing for transmitting the second data to another computer; processing for receiving, from another computer which acquires a second partial key 103 of the first user A, third data generated by implementing decryption processing by means of the second partial key 103 and implementing encryption processing by means of a public key of a second user B upon the second data; and processing for generating the first data encrypted by the public key of the second user B by implementing demasking processing on the third data by using a random number in accordance with the encryption system to be used.