CODEWITHSUNDEEP
c++clinuxlibconfig
Juliano Oliveira
Juliano Oliveira

Reputation: 926

Storing crypted data with libconfig

I'm using the libconfig to create an configuration file and one of the fields is a content of a encrypted file. The problem occurs because in the file have some escapes characters that causes a partial storing of the content. What is the best way to store this data to avoid accidental escapes caracter ? Convert to unicode? Any suggestion?

Upvotes: 4

Views: 266

Answers (2)

Serge Ballesta
Serge Ballesta

Reputation: 148965

The standard for encoding binary data in text used to be uuencode and is now base64. Both use same paradigm: a byte uses 8bits, so 3 bytes use 24 bits or 4 6 bits characters.

uuencode just used the 6 bits with an offset of 32 (ascii code for space), so characters are in range 32-96 => all in printable ascii range, but including space and possibly other characters that could have special meanings

base64 choosed these 64 characters to represent values from 0 to 63 (no =:;,'"\*(){}[] that could have special meaning...):

ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/

and the equal sign(=) being a place holder for empty positions and the end of an encoded string to ensure that the encoded string length is a multiple of 4.

Unfortunately, neither the C nor C++ standard library offer functions for uuencode not base 64 conversions, but you can find nice implementations around, with many pointers in this other SO answer: How do I base64 encode (decode) in C?

Upvotes: 2

dbush
dbush

Reputation: 224082

You can use either URL encoding, where each non-ASCII character is encoded as a % character followed by two hex digits, or you case use base64 encoding, where each set of 3 bytes is encoded to 4 ASCII characters (3x8 bits -> 4x6 bits).

For example, if you have the following bytes:

00 01 41 31 80 FE

You can URL encode it as follows:

%00%01A1%80%FE

Or you can base64 encode it like this, with 0-25 = A-Z, 26-51 = a-z, 52-62 = 0-9, 62 = ., 63 = /:

(00000000 00000001 01000001) (00110001 10000000 11111110) -->
(000000 000000 000101 000001) (001100 011000 000011 111110) 

AAJBNYD.

Upvotes: 2

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