Abstract: The invention concerns a multiple private key and secondary key cryptography method, including segmentation into blocks having a specific number of characters, and, for each block, a first step of encrypting each block with a first part of the multiple private key, determining an intermediate key specific to the block from the multiple private key and the secondary key, processing each block with at least one algorithm dependent on the intermediate key, said processing providing a processed block, and a second step of encrypting the processed block, and, for the set of blocks, forming a cryptogram including the processed blocks and characters representing the secondary key.