Cifrado privado/público en Python con biblioteca estándar

Question

¿Hay algún módulo que mi búsqueda no haya podido descubrir que permita escribir código como el siguiente? La razón para querer escribir código como este no es importante. Todo lo que busco es un código que tenga una API simple para generar claves de bytes públicas y privadas y para codificar y decodificar fácilmente datos con esas claves.

import module, os 

method, bits, data = 'RSA', 1024, os.urandom(1024) 
public, private = module.generate_keys(method, bits) 

assert isinstance(public, bytes) and isinstance(private, bytes) 
assert module.decode(module.encode(data, private), public) == data 
assert module.decode(module.encode(data, public), private) == data 

La mayor parte de lo que parece estar disponible requiere descargar un paquete y solo se ejecuta en Python 2.x. También es bastante común encontrar bibliotecas que trabajen con archivos PEM u otros tipos de certificados. Me gustaría evitar tener que lidiar con esos archivos, generar claves públicas y privadas sobre la marcha, y trabajar rápidamente con los datos en la memoria.

Answer 1

El cifrado de clave pública no se encuentra en la biblioteca estándar. Hay algunas bibliotecas de terceros en PyPi para él sin embargo:

• PyCrypto
• RSA Python

Si usted está interesado en las matemáticas detrás de ella, Python hace que sea fácil de experimentar:

code = pow(msg, 65537, 5551201688147)    # encode using a public key 
plaintext = pow(code, 109182490673, 5551201688147) # decode using a private key 

La generación de claves es un poco más complicada. Aquí hay un ejemplo simplificado de cómo hacer generación de claves en memoria usando urandom como fuente de entropía. El código se ejecuta en tanto Py2.6 y Py3.x:

import random 

def gen_prime(N=10**8, bases=range(2,20000)): 
    # XXX replace with a more sophisticated algorithm 
    p = 1 
    while any(pow(base, p-1, p) != 1 for base in bases): 
     p = random.SystemRandom().randrange(N) 
    return p 

def multinv(modulus, value): 
    '''Multiplicative inverse in a given modulus 

     >>> multinv(191, 138) 
     18 
     >>> 18 * 138 % 191 
     1 

    ''' 
    # http://en.wikipedia.org/wiki/Extended_Euclidean_algorithm 
    x, lastx = 0, 1 
    a, b = modulus, value 
    while b: 
     a, q, b = b, a // b, a % b 
     x, lastx = lastx - q * x, x 
    result = (1 - lastx * modulus) // value 
    return result + modulus if result < 0 else result 

def keygen(N): 
    '''Generate public and private keys from primes up to N. 

     >>> pubkey, privkey = keygen(2**64) 
     >>> msg = 123456789
     >>> coded = pow(msg, 65537, pubkey) 
     >>> plain = pow(coded, privkey, pubkey) 
     >>> assert msg == plain 

    ''' 
    # http://en.wikipedia.org/wiki/RSA 
    prime1 = gen_prime(N) 
    prime2 = gen_prime(N) 
    totient = (prime1 - 1) * (prime2 - 1) 
    return prime1 * prime2, multinv(totient, 65537) 

Answer 2

PyCrypto obras en Python 3 a partir de 2.4.1.

Answer 3

Aquí hay otro ejemplo

import random 


# RSA Algorithm 



ops = raw_input('Would you like a list of prime numbers to choose from (y/n)? ') 
op = ops.upper() 

if op == 'Y': 
    print """\n 2  3  5  7  11  13  17  19  23  29 
31  37  41  43  47  53  59  61  67  71 
73  79  83  89  97 101 103 107 109 113 
127 131 137 139 149 151 157 163 167 173 
179 181 191 193 197 199 211 223 227 229 
233 239 241 251 257 263 269 271 277 281 
283 293 307 311 313 317 331 337 347 349 
353 359 367 373 379 383 389 397 401 409 
419 421 431 433 439 443 449 457 461 463 
467 479 487 491 499 503 509 521 523 541 
547 557 563 569 571 577 587 593 599 \n""" 
    rsa() 
else: 
    print "\n" 
    rsa() 

def rsa(): 
    # Choose two prime numbers p and q 
    p = raw_input('Choose a p: ') 
    p = int(p) 

while isPrime(p) == False: 
    print "Please ensure p is prime" 
    p = raw_input('Choose a p: ') 
    p = int(p) 

q = raw_input('Choose a q: ') 
q = int(q) 

while isPrime(q) == False or p==q: 
    print "Please ensure q is prime and NOT the same value as p" 
    q = raw_input('Choose a q: ') 
    q = int(q) 

# Compute n = pq 
n = p * q 

# Compute the phi of n 
phi = (p-1) * (q-1) 

# Choose an integer e such that e and phi(n) are coprime 
e = random.randrange(1,phi) 

# Use Euclid's Algorithm to verify that e and phi(n) are comprime 
g = euclid(e,phi) 
while(g!=1): 
    e = random.randrange(1,phi) 
    g = euclid(e,phi) 

# Use Extended Euclid's Algorithm 
d = extended_euclid(e,phi) 

# Public and Private Key have been generated 
public_key=(e,n) 
private_key=(d,n) 
print "Public Key [E,N]: ", public_key 
print "Private Key [D,N]: ", private_key 

# Enter plain text to be encrypted using the Public Key 
sentence = raw_input('Enter plain text: ') 
letters = list(sentence) 

cipher = [] 
num = "" 

# Encrypt the plain text 
for i in range(0,len(letters)): 
    print "Value of ", letters[i], " is ", character[letters[i]] 

    c = (character[letters[i]]**e)%n 
    cipher += [c] 
    num += str(c) 
print "Cipher Text is: ", num 

plain = [] 
sentence = "" 

# Decrypt the cipher text  
for j in range(0,len(cipher)): 

    p = (cipher[j]**d)%n 

    for key in character.keys(): 
     if character[key]==p: 
      plain += [key] 
      sentence += key 
      break 
print "Plain Text is: ", sentence 

# Euclid's Algorithm 
def euclid(a, b): 
    if b==0: 
    return a 
else: 
    return euclid(b, a % b) 

# Euclid's Extended Algorithm 
def extended_euclid(e,phi): 
    d=0 
    x1=0 
    x2=1 
    y1=1 
    orig_phi = phi 
    tempPhi = phi 

while (e>0): 
    temp1 = int(tempPhi/e) 
    temp2 = tempPhi - temp1 * e 
    tempPhi = e 
    e = temp2 

    x = x2- temp1* x1 
    y = d - temp1 * y1 

    x2 = x1 
    x1 = x 
    d = y1 
    y1 = y 

    if tempPhi == 1: 
     d += phi 
     break 
return d 

# Checks if n is a prime number 
def isPrime(n): 
    for i in range(2,n): 
    if n%i == 0: 
     return False 
return True 

character = {"A":1,"B":2,"C":3,"D":4,"E":5,"F":6,"G":7,"H":8,"I":9,"J":10, 
    "K":11,"L":12,"M":13,"N":14,"O":15,"P":16,"Q":17,"R":18,"S":19, 
    "T":20,"U":21,"V":22,"W":23,"X":24,"Y":25,"Z":26,"a":27,"b":28, 
    "c":29,"d":30,"e":31,"f":32,"g":33,"h":34,"i":35,"j":36,"k":37, 
    "l":38,"m":39,"n":40,"o":41,"p":42,"q":43,"r":44,"s":45,"t":46, 
    "u":47,"v":48,"w":49,"x":50,"y":51,"z":52, " ":53, ".":54, ",":55, 
    "?":56,"/":57,"!":58,"(":59,")":60,"$":61,":":62,";":63,"'":64,"@":65, 
    "#":66,"%":67,"^":68,"&":69,"*":70,"+":71,"-":72,"_":73,"=":74}