Abstract: The method provided is for the encryption of data block by block, but unlike conventional methods like DES or AES, with a variable and substantially greater block length. The enciphering operations depend not only on the key, but also on the length of the plaintext blocks. The method meets the Strict Avalanche Criterion much better than conventional ciphers and blocks do not need to be padded. The method that additionally partitions outsized blocks executes the following steps: Derivation of the internal state of the method from the key, pseudorandom permutation of plaintext bits or groups of plaintext bits, partitioning of outsized plaintext data blocks, execution of at least three unbalanced Feistel network rounds with round functions having the ability to output results with variable length and bit-by-bit exclusive-or combination with output of round functions within the Feistel rounds.