Abstract: A method is provided for securing transmission data between an upload device and a download device. The upload device is configured to generate a first matrix, a second matrix and a re-encryption vector, to encrypt a plaintext data file using the first matrix to obtain a ciphertext data file, to transmit the ciphertext data file and the re-encryption vector to a server, and to transmit the second matrix to the download device. The server is configured to re-encrypt the ciphertext data file using the re-encryption vector to obtain a re-encrypted data file that can be decrypted using the second matrix to obtain a decrypted data file, and to allow the download device to download the re-encrypted data file therefrom.