A method and system for decoding an encrypted file. A recipient computer: receives, from a sender computer, the encrypted file having a filename that includes an encoded address; parses the received filename; extracts the encoded address from the parsed filename; accesses a voice check ticket at the extracted encoded address; receives voice check text from the voice check ticket; visually displays the received voice check text on a computer display of the recipient computer; prompts the recipient to read aloud the displayed voice check text; receives an audio signal from a reading aloud, by the prompted recipient, of the displayed voice check text; transmits the received audio signal to a server computer; receives, from the server computer, an encryption key after the server computer has verified, from analysis of the audio signal, the recipient's voice; and decrypts the received encrypted file using the received encryption key.