CTF crypto (I) some simple encoding and encryption

Base64

be used for http In the environment, the longer identification information

The basic rule

1. Change every three octets into four six bytes , Add two... To each byte high order 0, Examples are as follows ：
   01111001 01101111 01110101
   011110 010110 111101 110101
   00011110 00010110 00111101 00110101
   According to Base64 The alphabet gets the following characters
   e W 9 1
2. Every time 76 Characters plus a newline
3. Handle the last Terminator
   At the end of the end, you can't put together three bytes , Then take ’=' The symbol complements the four bytes that have not been completed after conversion

variant

URL improvement Base64 code , Fill at the end ’=‘ Number , And encode the ’+‘ and ’/‘ Change the number to ’-‘ and ’_’, So as to avoid URL The conversion of codec and database storage .
Regular expression improvements will ’+‘ and ’/‘ Changed to ’!‘ and ’-’

Idempotent encryption

A very simple encryption method , There are... Letters in English 26 That's why 2 Of 0、1、2、3、4 The power can express 31 A unit , The alphabetic sequence number encryption is represented by binary powers .
Such as $15=2^0+2^1+2^2+2^3$, So because O This letter is on the... Of the alphabet 15 position , So it can be binary idempotent 0123 To encrypt the presentation .

Fence code

Ordinary fence

Divide plaintext passwords into N In groups , Then start with the first word of each group , Connect the words in the same position in each group , Finally form a meaningless sentence .
Such as Ilovebutdontknow Divide into 4 A group of letters
Ilov ebut dont know
Then start with the first word of each group , Connect the words in the same position in each group .
ledk lbon ouno vttw
Finally form a meaningless sentence
ledklbonounovttw

W type

The string loveuloveu When grouping, the following W Type format
I . . . u . . . e .
. o . e . l . v . u
. . v . . . o . . .
Then link it together to form the following string lueoelvuvo
Decrypt by writing code , Or decrypt the following URL http://www.atoolbox.net/Tool.php?Id=777

Bacon code

A kind of use a,b Steganography in which two letters are used instead of the other letters .
Each letter corresponds to 5 individual $a,b$ A group of letters , Such as A/a - aaaaa