A proposed Mode for triple DES encryption

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A proposed mode for triple-DES encryption

We propose a new mode of multiple encryption-triple-DES external feedback
cipher block chaining with output feedback masking. The aim is to provide increased
protection against certain attacks (dictionary attacks and matching ciphertext attacks)
which exploit the short message-block size of DES. The new mode obtains this protection
through the introduction of secret masking values that are exclusive-ORed with the
intermediate outputs of each triple-DES encryption operation. The secret mask value is
derived from a fourth encryption operation per message block, in addition to the three used in previous modes. The new mode is part of a suite of encryption modes proposed in the ANSI X9.F.1 triple-DES draft standard (X9.52).

Introduction
Table 1 Abbreviations and definitions.
Table 2 Probability of exposing a single block.
Attacks against earlier schemes (Blaze
and Jones)
Internal feedback
Objectives of the new mode
Triple-DES external feedback CBC with OFB
masking (CBCM) mode
Strength of Triple-DES external feedback CBC
with OF6 masking (CBCM) mode
Triple-DES external feedback CBC with OFB masking (CBCM)
mode.
Remark on reusing the IV
Some design rationale
Properties of the present mode
Concluding remarks