# Cryptography



## MD5


### Scripts

- Hash length extension attack
- Brute force hex digest chars


### Command Line
```
$ echo -n password | md5sum
5f4dcc3b5aa765d61d8327deb882cf99
```

- 32 chars

```
7e1321b3c8423b30c1cb077a2e3ac4f0a2a551a6458a8de22446cc76d639a9e98fc42c6cddf9966db3b09e843650343578b04d5e377d298e78455efc5ca404d5f4c9385f1902f7334b00b9b4ecd164de8bf8854bebe108183caeb845c7676ae48fc42c6ddf9966db3b09e84365034357327a6c4304ad5938eaf0efb6cc3e53dc7ff9ea9a069bd793691c422fb818
```

- Use Python's md5.md5().digest()

- md5 hashes: [here](http://hash-killer.com/) and [here](http://www.md5this.com/)


------

## SHA


### Scripts
- SHA-256 brute force


### Command Line

- Brute force:
```
import hashlib, itertools
hash = '6307c5441ebac07051e3b90d53c3106230dd9aa128601dcd5f63efcf824ce1ba'
ch = 'abcdef0123456789'
for a, b, c, d, e, f in itertools.product(ch, ch, ch, ch, ch, ch):
    if hashlib.sha256('ASIS_a9%s00f497f2eaa4372a7fc21f0d' % (a + b + c + d + e + f)).hexdigest() == hash:
        print 'ASIS_a9%s00f497f2eaa4372a7fc21f0d' % (a + b + c + d + e + f)
```




--------

## Rotation Ciphers


### Scripts
- Caesar
- Brute force rotation
- Pygenere
- Frequency analysis


### Online tools:

- Frequency analysis: [here](http://www.simonsingh.net/The_Black_Chamber/hintsandtips.html) and [here](http://www.xarg.org/tools/caesar-cipher)

### In the command line

```sh
$ VAR=$(cat data.txt)
$ echo "$VAR"
$ alias rot13="tr A-Za-z N-ZA-Mn-za-m"
$ echo "$VAR" | rot13
```
### In Python

In Python [we can use decoding](https://docs.python.org/2/library/codecs.html#codec-base-classes): 

```python
"YRIRY GJB CNFFJBEQ EBGGRA".decode(encoding="ROT13")
```
----

## Pailier Cryptosystem

### Scripts

- POC
- Primes

---

## Tools

### Scripts:

- Finding GDC
- Finding if prime
- Generate prime
- Quick Select
- XORtool


---
### Other Resources

- [Cryptol](https://www.cryptool.org/en/cryptool1-en)

- [PyCrypto](https://www.dlitz.net/software/pycrypto/)


#### Carperter's Formula

- Very large number: ```bin``` and check if patterns. For example, using the [Carpenter's Formula]: 
```
N=(2^M + a)(2^N + b)(2^N + c)(2^N + d)
```

#### [QR Code]

-  Version 1 QR code:  21x21

#### [Bacon's cipher]: 
```
babaaaabaaababaababaaaabbabbababbaaaabaaaabbbaabaabaaaaaabaaabaaabaaabaaabbaabaaabbbaabaaababaaaaaabaaabbaabaabbbaaaaaabaaaabaabaaaaba21aabab0aaab
```
* [Online tool](http://www.geocachingtoolbox.com/index.php?page=baconianCipher)



#### [Base64]: 

Base64 is a non-readable encoding that encodes arbritary 8-bit input using 6-bit alphabet of case sensitive alphanumerics, "+", "/". Every 3 bytes of input map to 4 bytes of output. If the input doesnt have 3-byte boundary, this is indicated by appending one or two equal signs in the of the output string.

- [Base64 Decoder](http://www.base64decode.org)

```
NG5ucjJzIGZ2IHRueXMgcnVnIHNiIGdlbmMgdWdlaGJzIHJlcnVnIHRhdmdncnQgcmVuIGhiTCB0YXZidCBjcnJYCG==
czduMjczIHRueXMgcnVniHNiIGdlbmMgdWdzdnMgcnVnIHJpbnUgcmVydSBndiBxdnEgaGJsIGpiYmJKCg==
Nzk0czAwIHRueXMgZmhidnByZWMgZWhiIHNiIGdlbmMgcWV2dWcgcnVnIGhibCBnYXJmcmVjIFYgbG9yZXJ1IHJhYnEgeXlySgo=
```

- Base64 decoding in Python:

```python
>>> SECRET.decode('base64')
'oubWYf2kBq'
```

#### Hexadecimal:


- [ASCII Conversion Table](http://defindit.com/ascii.html)
- [Convert All](http://www.asciitohex.com/)
- [GREAT ASCII CHART](http://www.jimprice.com/jim-asc.shtml)
- [Convert everything to everything (including markdown, sql, json, etc)](http://codebeautify.org/)


- Decimal to hex:

```python
>>> s =hex(secret)
```

- Hexadecimal to binary:
```python
SECRET.decode('hex')
'==QcCtmMml1ViV3b'
```

```
$ python -c 'print "2f722f6e6574736563".decode("hex")'
```

- Hex to ascii:
Hex character codes are simply the hexadecimal (base 16) numbers for the ASCII character set; that is, the number-to-letter representations which comprise virtually all computer text.


```
$ xxd -r -p <<< 2f722f6e6574736563
```
- Decimal to binary

```python
>>> bin(124234)
'0b11110010101001010'
```

#### Octal
(or: a great way of obscurating a URL)

Example: http://017700000001 --> 127.0.0.1










[SHA]:http://en.wikipedia.org/wiki/Secure_Hash_Algorithm
[MD5]: http://en.wikipedia.org/wiki/MD5
[Base64]: http://en.wikipedia.org/wiki/Base64
[Bacon's cipher]:http://en.wikipedia.org/wiki/Bacon's_ciphe
[Carpenter's Formula]:http://security.cs.pub.ro/hexcellents/wiki/writeups/asis_rsang
[pngcheck]: http://www.libpng.org/pub/png/apps/pngcheck.html
[karmadecay]: http://karmadecay.com/
[tineye]:  https://www.tineye.com/
[images.google.com]: https://images.google.com/?gws_rd=ssl
[base64 decoding]: http://www.motobit.com/util/base64-decoder-encoder.asp
[pnginfo]: http://www.stillhq.com/pngtools/
[namechk]: http://namechk.com
[QR Code]: http://en.wikipedia.org/wiki/QR_code