Re: GRUB and boot partition
- Date: Wed, 3 Jan 2018 10:59:33 -0800
- From: David Christensen <dpchrist@xxxxxxxxxxxxxxxx>
- Subject: Re: GRUB and boot partition
On 01/03/18 06:45, Gary Dale wrote:
On 2018-01-02 02:35 PM, Pascal Hambourg wrote:
Encryption does not require extra space (except for header and
block padding). Encrypted data have the same size of cleartext data.
Encryption is similar in concept to compression.
AFAIK common use on Debian systems:
1. Encryption functions  are reversible functions that transform
data 1:1 in size, and are lossless.
2. Compression functions  are reversible functions that strive for
size ratios of N:1, where N > 1 (uncompressed:compressed), and can be
lossless or lossly.
A related topic is hashing functions  (N:fixed, can be difficult to
It could even reduce the space requirements.
I'm curious -- can you cite a compressing cipher code that cannot be
reduced to independent compression and cipher functions?
Encryption and compression both work by replacing strings of letters with something else.
I agree that encryption and compression are both forms of coding .
Encryption and compression both work by replacing strings of letters
with something else. What we call clear text, for example, is just a > Caesar cipher where each letter is replaced by a number (its ASCII code
ASCII  is a transliteration code -- replace a token from one alphabet
(Roman letters, Arabic numerals, common English symbols, etc.) with a
token from another alphabet (7-bit binary number). Spelling, grammar,
and meaning are unchanged.
The goal of a substitution cipher is to conceal meaning, and can be done
without changing alphabets (e.g. rot13 ). Spelling and grammar are
unchanged (which facilitates cryptanalysis).
Morse code, on the other hand, replaces common letters with
shorter sequences of dots and dashes than less common letters.
I agree that Morse Code  uses frequency-based techniques.