Method and apparatus for secure data transmission via network

A method for making an electronic exchange of an original image of written information read out of a recording medium between a data transmission side and a data reception side via a network, comprising:

• a data transmission step;
• and
• a data reception step;
• said data transmission step including:
• a first step of applying digital signature to said original image so as to produce first signed data;
• a second step of ciphering said first signed data with a private key of said data reception side so as to produce a ciphered signed data;
• a third step of merging said original image data and said first signed data, applying a one-way function to obtained merged data, and ciphering an output of said one-way function with a secret key of said data transmission side so as to obtain second signed data;
• and
• a fourth step of transmitting said original image data, said second signed data and said ciphered signed data to said data reception side;
• said data reception step including:
• a fifth step of obtaining said original image data, said second signed data and said ciphered signed data;
• a sixth step of enciphering said obtained ciphered signed data with a secret key of said data reception side so as to obtain third signed data;
• a seventh step of merging said obtained original image data and said third signed data and applying a one-way function to obtained merged data;
• an eighth step of enciphering said received second signed data with a private key of said data transmission side;
• and
• a ninth step of comparing results of said steps 8 and 9 so as to confirm data validity.

A data transmission apparatus comprising:

• first ciphering means for receiving an electronic image of an original image and a first secret key as inputs, and outputting a first digital signature obtained by ciphering said electronic image with said first secret key;
• processing means for receiving said electronic image as input, and outputting a partial or processed image of said electronic image;
• second ciphering means for receiving said partial or processed image, said first digital signature and a second secret key as inputs, merging said partial or processed image and said first digital signature, ciphering obtained merged data with said second secret key, and outputting an obtained second digital signature;
• third ciphering means for receiving said first digital signature and a private key as inputs, and obtaining ciphered data of said first digital signature with said private key;
• and
• transmitting means for transmitting said partial or processed image, said second digital signature, and said ciphered data of said first signature to an external data channel.