appliedcrypto/possible_ans.md at 44789e8d3afa8b0e25d3beaa2d9cfe31b2329707

applied-cryptography/appliedcrypto

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billbuchanan 44789e8d3a Update

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Commands in Section A:

openssl list-cipher-commands
openssl version
openssl prime –hex 1111
openssl enc -aes-256-cbc -in myfile.txt -out encrypted.bin
openssl enc -aes-256-cbc -in myfile.txt -out encrypted.bin –base64
openssl enc -d -aes-256-cbc -in encrypted.bin -pass pass:napier -base64

A.1

$ openssl list-cipher-commands
aes-128-cbc
aes-128-ecb
aes-192-cbc
aes-192-ecb
aes-256-cbc
aes-256-ecb
base64
bf
bf-cbc
bf-cfb
bf-ecb
bf-ofb
camellia-128-cbc
camellia-128-ecb
camellia-192-cbc
camellia-192-ecb
camellia-256-cbc
camellia-256-ecb
cast
cast-cbc
cast5-cbc
cast5-cfb
cast5-ecb
cast5-ofb
des
des-cbc
des-cfb
des-ecb
des-ede
des-ede-cbc
des-ede-cfb
des-ede-ofb
des-ede3
des-ede3-cbc
des-ede3-cfb
des-ede3-ofb
des-ofb
des3
desx
rc2
rc2-40-cbc
rc2-64-cbc
rc2-cbc
rc2-cfb
rc2-ecb
rc2-ofb
rc4
rc4-40
seed
seed-cbc
seed-cfb
seed-ecb
seed-ofb

And:

napier@napier-virtual-machine:~$ openssl version
OpenSSL 1.0.2g  1 Mar 2016

A.3

napier@napier-virtual-machine:~$ nano myfile.txt
napier@napier-virtual-machine:~$ openssl enc -aes-256-cbc -in myfile.txt -out encrypted.bin
enter aes-256-cbc encryption password: napier
Verifying - enter aes-256-cbc encryption password: 
napier@napier-virtual-machine:~$ cat encrypted.bin 
Salted__<12><>kBֿ<42><D6BF>O<EFBFBD>;<3B>|`<02>"<22><><EFBFBD><EFBFBD>ե
napier@napier-virtual-machine:~$ openssl enc -d -aes-256-cbc -in encrypted.bin
enter aes-256-cbc decryption password: napier
Hello

A.4

napier@napier-virtual-machine:~$ openssl enc -aes-256-cbc -in myfile.txt -out encrypted.bin -base64
enter aes-256-cbc encryption password:
Verifying - enter aes-256-cbc encryption password:
napier@napier-virtual-machine:~$ cat encrypted.bin 
U2FsdGVkX18Z7N1ZzT9+up7rmoTInUto8HAflAvIEPE=
napier@napier-virtual-machine:~$ openssl enc -d -aes-256-cbc -in encrypted.bin -base64
enter aes-256-cbc decryption password: napier
Hello

A.7

We can use the -bf-cbc option for Blowfish:

openssl enc -bf-cbc -in myfile.txt -out encrypted1.bin 
openssl enc -d -bf-cbc -pass pass:password -in encrypted1.bin

A sample run is:

$ openssl enc -bf-cbc -in myfile.txt -out encrypted1.bin 
enter bf-cbc encryption password: password
Verifying - enter bf-cbc encryption password: password
$ openssl enc -d -bf-cbc -pass pass:password -in encrypted1.bin 
Hello

B.2

You may need to install "Crypto" with:

pip install pycrypto

And Padding with:

pip install padding

from Crypto.Cipher import AES
import hashlib
import sys
import binascii
import Padding

val='hello'
password='hello'

plaintext=val

def encrypt(plaintext,key, mode):
	encobj = AES.new(key,mode)
	return(encobj.encrypt(plaintext))

def decrypt(ciphertext,key, mode):
	encobj = AES.new(key,mode)
	return(encobj.decrypt(ciphertext))

key = hashlib.sha256(password).digest()


plaintext = Padding.appendPadding(plaintext,blocksize=Padding.AES_blocksize,mode='CMS')
print "After padding (CMS): "+binascii.hexlify(bytearray(plaintext))

ciphertext = encrypt(plaintext,key,AES.MODE_ECB)
print "Cipher (ECB): "+binascii.hexlify(bytearray(ciphertext))

plaintext = decrypt(ciphertext,key,AES.MODE_ECB)
plaintext = Padding.removePadding(plaintext,mode='CMS')
print "  decrypt: "+plaintext


plaintext=val


plaintext = Padding.appendPadding(plaintext,blocksize=Padding.AES_blocksize,mode='ZeroLen')
print "\nAfter padding (Bit): "+binascii.hexlify(bytearray(plaintext))

ciphertext = encrypt(plaintext,key,AES.MODE_ECB)
print "Cipher (ECB): "+binascii.hexlify(bytearray(ciphertext))

plaintext = decrypt(ciphertext,key,AES.MODE_ECB)
plaintext = Padding.removePadding(plaintext,blocksize=Padding.AES_blocksize,mode='ZeroLen')
print "  decrypt: "+plaintext


plaintext=val

plaintext = Padding.appendPadding(plaintext,blocksize=Padding.AES_blocksize,mode='Space')
print "\nAfter padding (Null): "+binascii.hexlify(bytearray(plaintext))

ciphertext = encrypt(plaintext,key,AES.MODE_ECB)
print "Cipher (ECB): "+binascii.hexlify(bytearray(ciphertext))

plaintext = decrypt(ciphertext,key,AES.MODE_ECB)
plaintext = Padding.removePadding(plaintext,blocksize=Padding.AES_blocksize,mode='Space')
print "  decrypt: "+plaintext


plaintext=val

plaintext = Padding.appendPadding(plaintext,blocksize=Padding.AES_blocksize,mode='Random')
print "\nAfter padding (Random): "+binascii.hexlify(bytearray(plaintext))

ciphertext = encrypt(plaintext,key,AES.MODE_ECB)
print "Cipher (ECB): "+binascii.hexlify(bytearray(ciphertext))

plaintext = decrypt(ciphertext,key,AES.MODE_ECB)
plaintext = Padding.removePadding(plaintext,mode='Random')
print "  decrypt: "+plaintext

C.2

from Crypto.Cipher import DES
import hashlib
import sys
import binascii
import Padding

val='hello'
password='hello'

plaintext=val


def encrypt(plaintext,key, mode):
	encobj = DES.new(key,mode)
	return(encobj.encrypt(plaintext))

def decrypt(ciphertext,key, mode):
	encobj = DES.new(key,mode)
	return(encobj.decrypt(ciphertext))


print "\nDES"
key = hashlib.sha256(password).digest()[:8]

plaintext = Padding.appendPadding(plaintext,blocksize=Padding.DES_blocksize,mode='CMS')
print "After padding (CMS): "+binascii.hexlify(bytearray(plaintext))

ciphertext = encrypt(plaintext,key,DES.MODE_ECB)
print "Cipher (ECB): "+binascii.hexlify(bytearray(ciphertext))

plaintext = decrypt(ciphertext,key,DES.MODE_ECB)
plaintext = Padding.removePadding(plaintext,mode='CMS')
print "  decrypt: "+plaintext

D.1

from Crypto.Cipher import AES
import hashlib
import sys
import binascii
import Padding

val='hello'
password='hello'

if (len(sys.argv)>1):
	val=sys.argv[1]

if (len(sys.argv)>2):
	password=sys.argv[2]

plaintext=val

def encrypt(plaintext,key, mode):
	encobj = AES.new(key,mode)
	return(encobj.encrypt(plaintext))

def decrypt(ciphertext,key, mode):
	encobj = AES.new(key,mode)
	return(encobj.decrypt(ciphertext))

key = hashlib.sha256(password).digest()


plaintext = Padding.appendPadding(plaintext,blocksize=Padding.AES_blocksize,mode='CMS')
print "After padding (CMS): "+binascii.hexlify(bytearray(plaintext))

ciphertext = encrypt(plaintext,key,AES.MODE_ECB)
print "Cipher (ECB): "+binascii.hexlify(bytearray(ciphertext))

plaintext = decrypt(ciphertext,key,AES.MODE_ECB)
plaintext = Padding.removePadding(plaintext,mode='CMS')
print "  decrypt: "+plaintext


plaintext=val

A sample run is:

napier@napier-virtual-machine:~$ python d1.py hello hello123
After padding (CMS): 68656c6c6f0b0b0b0b0b0b0b0b0b0b0b
Cipher (ECB): 0a7ec77951291795bac6690c9e7f4c0d
  decrypt: hello
napier@napier-virtual-machine:~$ python d1.py inkwell orange
After padding (CMS): 696e6b77656c6c090909090909090909
Cipher (ECB): 484299ceec1ad83b1ce848b0a9733c8d
  decrypt: inkwell
napier@napier-virtual-machine:~$ python d1.py security qwerty
After padding (CMS): 73656375726974790808080808080808
Cipher (ECB): 6be35165e2c9a624de4f401692fe7161
  decrypt: security
napier@napier-virtual-machine:~$ python d1.py Africa changme
After padding (CMS): 4166726963610a0a0a0a0a0a0a0a0a0a
Cipher (ECB): ab453ac52cd3b1a61b35d6e85e4568f8
  decrypt: Africa

D.2

Sample code is:

from Crypto.Cipher import DES
import hashlib
import sys
import binascii
import Padding

val='hello'
password='hello'

if (len(sys.argv)>1):
	val=sys.argv[1]

if (len(sys.argv)>2):
	password=sys.argv[2]

plaintext=val

def encrypt(plaintext,key, mode):
	encobj = DES.new(key,mode)
	return(encobj.encrypt(plaintext))

def decrypt(ciphertext,key, mode):
	encobj = DES.new(key,mode)
	return(encobj.decrypt(ciphertext))

key = hashlib.sha256(password).digest()


plaintext = Padding.appendPadding(plaintext,blocksize=Padding.DES_blocksize,mode='CMS')
print "After padding (CMS): "+binascii.hexlify(bytearray(plaintext))

ciphertext = encrypt(plaintext,key[:8],DES.MODE_ECB)
print "Cipher (ECB): "+binascii.hexlify(bytearray(ciphertext))

plaintext = decrypt(ciphertext,key[:8],DES.MODE_ECB)
plaintext = Padding.removePadding(plaintext,mode='CMS')
print "  decrypt: "+plaintext


plaintext=val

A sample run is:

napier@napier-virtual-machine:~$ python d2.py hello hello123
After padding (CMS): 68656c6c6f030303
Cipher (ECB): 8f770898ddb9fb38
  decrypt: hello
napier@napier-virtual-machine:~$ python d2.py inkwell orange
After padding (CMS): 696e6b77656c6c01
Cipher (ECB): 1086a73ab5273254
  decrypt: inkwell
napier@napier-virtual-machine:~$ python d2.py security qwerty
After padding (CMS): 73656375726974790808080808080808
Cipher (ECB): d19c86b3fc7e924f148652c183caa922
  decrypt: security
napier@napier-virtual-machine:~$ python d2.py Africa changeme
After padding (CMS): 4166726963610202
Cipher (ECB): 6e11929fe6a3c081
  decrypt: Africa

D.3

Answer:

/vA6BD+ZXu8j6KrTHi1Y+w== - italy

from Crypto.Cipher import AES
import hashlib
import sys
import binascii
import Padding
import base64

val='fox'
password='hello'
cipher=''

import sys

if (len(sys.argv)>1):
	cipher=(sys.argv[1])
if (len(sys.argv)>2):
	password=(sys.argv[2])

plaintext=val

def encrypt(plaintext,key, mode):
	encobj = AES.new(key,mode)
	return(encobj.encrypt(plaintext))

def decrypt(ciphertext,key, mode):
	encobj = AES.new(key,mode)
	return(encobj.decrypt(ciphertext))

key = hashlib.sha256(password).digest()

cipher='/vA6BD+ZXu8j6KrTHi1Y+w=='

ciphertext = base64.b64decode(cipher)
plaintext = decrypt(ciphertext,key,AES.MODE_ECB)
print plaintext
plaintext = Padding.removePadding(plaintext,mode='CMS')
print "  decrypt: "+plaintext


plaintext=val

E.1

Answers:

germany
france
england
scotland

Possible solution for E.1:

from Crypto.Cipher import AES
import hashlib
import sys
import binascii
import Padding

val='fox'
password='hello'
cipher='b436bd84d16db330359edebf49725c62'

import sys

if (len(sys.argv)>1):
	cipher=(sys.argv[1])
if (len(sys.argv)>2):
	password=(sys.argv[2])

plaintext=val

def encrypt(plaintext,key, mode):
	encobj = AES.new(key,mode)
	return(encobj.encrypt(plaintext))

def decrypt(ciphertext,key, mode):
	encobj = AES.new(key,mode)
	return(encobj.decrypt(ciphertext))

key = hashlib.sha256(password).digest()


ciphertext=binascii.unhexlify(cipher)

plaintext = decrypt(ciphertext,key,AES.MODE_ECB)
print ('Cipher: '+ cipher)
print ('Password: '+ password)
plaintext = Padding.removePadding(plaintext,mode='CMS')
print ("  decrypt: "+plaintext)

A sample run gives:

Cipher: b436bd84d16db330359edebf49725c62
Password: hello
  decrypt: germany

E.2

Answers:

germany
france
england
scotland

DES uses a 64-bit key, of which we have use 56 bits for the actual key. We thus need to truncate our SHA-256 generated key, down to a 64-bit key. We can do that in Python with [:8]. A possible solution for E.2:

from Crypto.Cipher import DES
import hashlib
import sys
import binascii
import Padding

val='fox'
password='hello'
cipher=''

import sys

def encrypt(plaintext,key, mode):
	encobj = DES.new(key,mode)
	return(encobj.encrypt(plaintext))

def decrypt(ciphertext,key, mode):
	encobj = DES.new(key,mode)
	return(encobj.decrypt(ciphertext))

key = hashlib.sha256(password).digest()


ciphertext=binascii.unhexlify("f37ee42f2267458d")

plaintext = decrypt(ciphertext,key[:8],DES.MODE_ECB)
print plaintext

plaintext = Padding.removePadding(plaintext,mode='CMS')
print "  decrypt: "+plaintext


plaintext=val

F.1

Plaintext: norway

Key: changeme

A sample code is:

from Crypto.Cipher import AES
import hashlib
import sys
import binascii
import Padding
import base64

def decrypt(ciphertext,key, mode):
	encobj = AES.new(key,mode)
	return(encobj.decrypt(ciphertext))

pw = ["hello","ankle","changeme","123456"]

c='1jDmCTD1IfbXbyyHgAyrdg=='

for password in pw:

	try:
		key = hashlib.sha256(password).digest()
		cipherhex = base64.b64decode(c).encode('hex')
		ciphertext = binascii.unhexlify(cipherhex)

		print "Cipher (ECB): "+binascii.hexlify(bytearray(ciphertext))

		plaintext = decrypt(ciphertext,key,AES.MODE_ECB)
		plaintext = Padding.removePadding(plaintext,mode='CMS')
		print "  decrypt: "+plaintext
		print "  Key found: "+password

	except:	
		print(".")

G.1

Answers:

e47a2bfe646a - orange
ea783afc66 - apple
e96924f16d6e - banana

Just convert the hex value to a byte array:

var chacha20 = require("chacha20");
var crypto = require('crypto');

var keyname="qwerty";

var key = crypto.createHash('sha256').update(keyname).digest();

var nonce = new Buffer.alloc(8);

nonce.fill(0);

console.log( key);

var ciphertext="e96924f16d6e" 
// var ciphertext="ea783afc66"
// var ciphertext="e47a2bfe646a"

console.log("Ciphertext:\t",ciphertext);

console.log("Decipher\t",chacha20.decrypt(key,nonce, new Buffer(ciphertext,"hex")).toString());

A sample run is:

$ npm install chacha20
$ cat fruit.js
var chacha20 = require("chacha20");
var crypto = require('crypto');

var keyname="qwerty";

var key = crypto.createHash('sha256').update(keyname).digest();

var nonce = new Buffer.alloc(8);

nonce.fill(0);

console.log( key);

var ciphertext="e96924f16d6e" 
// var ciphertext="ea783afc66"
// var ciphertext="e47a2bfe646a"

console.log("Ciphertext:\t",ciphertext);

console.log("Decipher\t",chacha20.decrypt(key,nonce, new Buffer(ciphertext,"hex")).toString())

$ node fruit.js

Ciphertext:	 e96924f16d6e
Decipher	 banana

G.2

Answers:

8d1cc8bdf6da - orange
911adbb2e6dda57cdaad - strawberry
8907deba - kiwi

// RC4

var crypto = require('crypto');

var keyname="napier";

var key = crypto.createHash('sha256').update(keyname).digest();

var cipher = crypto.createCipheriv('rc4', key,'' );
var ciphertext = '8d1cc8bdf6da'
console.log("Ciphertext:\t",ciphertext);


var decipher = crypto.createDecipheriv('rc4', key,'' );
var text = decipher.update( new Buffer(ciphertext,"hex"), 'hex','utf8');
console.log("Decipher:\t",text);

A sample run is:

$ nano fruit2.js
$ cat fruit2.js
var crypto = require('crypto');

var keyname="napier";

var key = crypto.createHash('sha256').update(keyname).digest();

var cipher = crypto.createCipheriv('rc4', key,'' );
var ciphertext = '8d1cc8bdf6da'
console.log("Ciphertext:\t",ciphertext);


var decipher = crypto.createDecipheriv('rc4', key,'' );
var text = decipher.update( new Buffer(ciphertext,"hex"), 'hex','utf8');
console.log("Decipher:\t",text);

$ node fruit2.js 
Ciphertext:	 8d1cc8bdf6da
Decipher:	 orange

14 KiB Raw Blame History Unescape Escape

A.1

A.3

A.4

A.7

B.2

C.2

D.1

D.2

D.3

E.1

E.2

F.1

G.1

G.2

14 KiB

Raw Blame History