Normally, the IDEA operates on 64-bit blocks using a 128-bit user-selected secret key. Out of this 128-bit key fifty two key subblocks of 16-bit are generated and used in the encryption process. The 52 16-bit key subblocks needed in decryption are computed from the encryption key subblocks. In the modified mode of encryption/decryption by means of the IDEA algorithm the user does not select the 128-bit key but chooses directly the 52 16-bit key subblocks for encryption and employs them as a secret key. In this way IDEA can protect a 64-bit block of data using 832-bit key. By making this new secret key partly public we can encipher/decipher by means of the IDEA using a key of an arbitrary length, but no longer than 832 bits.