It is proposed that simple substitution, applied both before and after encipherment by the Data Encryption Standard (DES) cipher, will make that encryption safe against an exhaustive key-search attack based on the DES key.

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).

Foiling an exhaustive key-search attack

A proposed mode for triple-DES encryption

A first data source and a second data source are combined into a complex intermediate form or result; the first data source can be extracted from the intermediate form using the second data source. The combining mechanism can provide an alternative to the exclusive-OR combiner commonly used in stream ciphers. Each data value from the first data source is transformed by substitution using one of potentially multiple translation tables (12). The translations within each table can be changed after each substitution operation using a changes controller (18). Commonly, the just-used table is re-arranged or permuted; permutation retains invertibility, so that the ciphertext may be deciphered. As a particular design, the just-used substitution element may be exchanged with some element within the same table, as selected by the second data source, after every translation. The combiner substitution tables (12) can easily be forced to be invertible, and when they are, extraction is possible by substitution through inverse tables (24). Valid inverse tables can be maintained provided that the same second data is used by both mechanisms. This is the normal situation in stream ciphers. The combiner can also be used to combine two pseudo-random confusion streams into a more-complex confusion stream. In this case, exctraction may be unnecessary and so the combiner substitution tables need not be invertible. Thus, the translation changes need not be limited to permutations.

Dynamic substitution combiner and extractor

(t,m) [?]. (t, n) [?, ?]. $10.00 [?]. $12.00 [?]. 128 [?]. $139.99 [?]. $15.00 [?]. $16.95 [?]. $16.96 [?]. $18.95 [?]. $24.00 [?]. $24.00/$34 [?]. $24.95 [?, ?]. $26.95 [?]. $29.95 [?]. $30.95 [?]. $39 [?]. $43.39 [?]. $45.00 [?]. $5.95 [?]. $54.00 [?]. $54.95 [?]. $54.99 [?]. $6.50 [?]. $6.95 [?]. $69.00 [?]. $69.95 [?]. $75.00 [?]. $89.95 [?]. th [?]. A [?]. A [?, ?]. χ [?]. H [?]. k [?, ?]. M [?, ?]. M [?]. n [?, ?, ?].

/pdf/a-complete-bibliography-of-publications-in-cryptologia-19afbi1vz2.pdf

A Complete Bibliography of Publications in Cryptologia

The introduction of public key crypto-systems has opened the way to using security in distributed applications without imposing huge management overhead. Electronic mail is one area where security is important. Privacy Enhanced Mail is emerging as a de-facto international standard for the interchange of secure e-mail.This paper discusses some of the current problematic issues of PEM and introduces a PEM User Agent developed to test some of its concepts. A number of PEM design and implementation issues are explained and a conclusion on the future directions of PEM and other related work is given.

Foiling an exhaustive key-search attack

Citations

A proposed mode for triple-DES encryption

Dynamic substitution combiner and extractor

A Complete Bibliography of Publications in Cryptologia

Privacy enhanced mail design and implementation perspectives

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