Talking safe using RSA, pycrypto and python

Usr6 · February 4, 2014

Criptografia asimetric? este un tip de criptografie care utilizeaza o pereche de chei: o cheie public? ?i o cheie privat?. Un utilizator care de?ine o astfel de pereche î?i public? cheia public? astfel încat oricine dore?te s? o poata folosi pentru a îi transmite un mesaj criptat. Numai de?in?torul cheii secrete (private) este cel care poate decripta mesajul astfel criptat.

Matematic, cele dou? chei sunt legate, îns? cheia privat? nu poate fi ob?inut? din cheia public?. In caz contrar, orcine ar putea decripta mesajele destinate unui alt utilizator, fiindc? oricine are acces la cheia public? a acestuia.

O analogie foarte potrivit? pentru proces este folosirea cutiei po?tale. Oricine poate pune în cutia po?tal? a cuiva un plic, dar la plic nu are acces decât posesorul cheii de la cutia po?tal?. [wikipedia: Criptografie asimetric? - Wikipedia ]

1.0 Generarea cheilor publice si private:

Pentru a putea comunica in secret Ion si Maria trebuie sa-si genereze cheile de criptare folosind scriptul de mai jos.

from Crypto.PublicKey import RSA

from Crypto import Random

print "Generating keys\nplease wait..."

# generare key pub/priv

random_generator = Random.new().read

key = RSA.generate(1024, random_generator)

public_key = key.publickey().exportKey("PEM")

private_key = key.exportKey("PEM")

keyfile = open("key.txt", "a")

keyfile.write(public_key)

keyfile.write("\n")

keyfile.write(private_key)

keyfile.close()

print "done."

Dupa rularea scriptului, Ion va gasi in fisierul key.txt :

iar Maria:

1.1 Key exchange:

Ion trebuie sa ii dea Mariei cheia lui publica si Maria trebuie sa-i dea lui Ion cheia ei publica

Ion: Marioooooooooooooooooooo, ia de aici cheia mea sa-mi poti scrie :

Maria: Multumesc Ioane, iti dau si eu cheitza mea:

1.2 Encrypting message:


from Crypto.PublicKey import RSA
from Crypto.Cipher import PKCS1_OAEP

mesaj = "Draga Ion, cei de pe http://rstforums.com au cheia mai lunga o au de 4096."

pub_key ="""-----BEGIN PUBLIC KEY-----
MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCjH4ZhGcvrs1iDF8Mk4rin90vB
kQyklff9gVItswpNpMzw7OhpMqOXk0BgQS4ROh3uEgp/fpi4ZhHJfYY9RBMTPdNc
IXUVv6TzcqSsarhiRUwmkZiBqPYGiqXG0ODSk0ROVo+0DhA/Lf5KPGGo0MREjqLE
WWahtz7gDUXI9rRnXwIDAQAB
-----END PUBLIC KEY-----"""

rsakey = RSA.importKey(pub_key)
rsakey = PKCS1_OAEP.new(rsakey)
encrypted = rsakey.encrypt(mesaj)
mesaj_criptat = encrypted.encode('base64')
print mesaj_criptat

1.2.1 Sending encrypted message

Maria: OctEHiY1wkK6My4YeogpXFH/Q+p/CdjuWxDljcgDS8EGVB0OpUHMjC91OntWUjgW0kph529CDAU/

Hg1I1kPVmOuV1AR3MNZ9exibIJPOcsKXl5j1WH/YhNNGRUOwzGJ2PxVNzoV2KibmMjRiLVYFw/OX

swUhIlCai08KQuFUgzA=

Ion: decrypting...

1.3 Decrypting message:


from Crypto.PublicKey import RSA
from Crypto.Cipher import PKCS1_OAEP 
from base64 import b64decode

mesaj_criptat = """OctEHiY1wkK6My4YeogpXFH/Q+p/CdjuWxDljcgDS8EGVB0OpUHMjC91OntWUjgW0kph529CDAU/
Hg1I1kPVmOuV1AR3MNZ9exibIJPOcsKXl5j1WH/YhNNGRUOwzGJ2PxVNzoV2KibmMjRiLVYFw/OX
swUhIlCai08KQuFUgzA="""

priv_key = """-----BEGIN RSA PRIVATE KEY-----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-----END RSA PRIVATE KEY-----"""
rsakey = RSA.importKey(priv_key) 
rsakey = PKCS1_OAEP.new(rsakey) 
decrypted = rsakey.decrypt(b64decode(mesaj_criptat)) 
print decrypted
print "press any key to exit..."
raw_input()

1.4 Concluzie:

Nu folositi chei scurte si mesaje lungi.

Later on that day...

Ion: urs eshti?

Ion: scuze, usr

Usr_6: nu

Ion: frate, zi shi mie cum sa-mi lungesc cheia?

Usr_6: prinzi un capat in menghina si cu patentu tragi de celalalt, dc?

Ion: nu cheia de la usa frate.. aia de la RSA, din tutorialul postat de tine pe RST

Usr_6: schimbi "key = RSA.generate(1024, random_generator)" cu "key = RSA.generate(2048, random_generator)" sau cat o vrei tu de lunga

In alte roluri:

Python 2.7.6 Release

https://www.dlitz.net/software/pycrypto/

Python and cryptography with pycrypto | Laurent Luce's Blog

https://launchkey.com/docs/api/encryption

nedo · February 5, 2014

Cred ca ar fi cazul ca incerc si eu pythone, ca parca se folosesc mai usor si instaleaza mai usor librariile decat in c++, sau mi se pare mie?

Ps. Frumos tutorial. Iar pentru cei care vor sa foloseasca un program de chat care are la baza ideea de aici sa verifice la mine in semnatura

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Talking safe using RSA, pycrypto and python

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