How do I decrypt using hashlib in python?

Question

I know how to encrypt:

encrypted = hashlib.sha256('1234').hexdigest()

But I am not sure, how to decrypt this?

decrypted = decrypt(encrypted)

Answer 1

The short answer is you cannot 'decrypt' a hash; it is a one way function. There is a major difference between encrypting and hashing.

Hashing

See http://en.wikipedia.org/wiki/Cryptographic_hash_function

Note: It is possible to 'BREAK' certain hashing algorithms, but this is not decrypting. You'll find more information in the links as well as other algorithms that are also supported by python

Encryption

and http://en.wikipedia.org/wiki/Encryption

Example

A useful example of hashing is storing passwords in a database whereas a useful example of encryption is sending your bank details to an online store to purchase something.

Answer 2

This is a valid question, maybe not posed correctly though.

OP, I think what you're trying to do is check a hashed value against an unhashed one?

hashed = hashlib.sha256('1234').hexdigest()
hashedstring = '1234' + ',' + hashed

now to check that hashed == original value. So parse out the piece before and after the comma. Hash 1234 and compare it to the value hashed.

def check_secure_val(h):
    commapos = h.find(",")
    val = h[0:commapos]
    hashval = h[commapos+1:-1]
    rehashval = hash_str(val)
    if rehashval == hashval:
        return val

where input h is a string of format "val,(HASHEDSTRING)"

and hash_str is a function that hashes.

Answer 3

The hashes are calculated using one way functions, i.e. it will give same output for a particular input but as it is only a one-way function, no matter what you do, you cannot decrypt it. One can try decrypting it by brute force, i.e calculating hashes of words from dictionary and comparing it with the hash you want to decrypt. To save the time of calculating the hashes of dictionary words, there are rainbow tables available online which contains hashes with the words.

read: http://en.wikipedia.org/wiki/Rainbow_table

You can also use online services for brute force decryption of a hash. there are plenty available and works well if the word you want to decrypt belongs to a dictionary.

Answer 4

Not-very-exact Analogy: Encryption is like someone wearing a disguise ... taking a Hash is like taking their fingerprints !

You can get the "original" person back by removing/reversing the disguise, but you cannot do that from a set of fingerprints !

Answer 5

this might help?

import hashlib

l = ["riyad", "onni", "arman"]

def check_user(h):
    for i in l:
        if h == hashlib.md5(i.encode('utf-8')).hexdigest():
            return i


print(check_user(hashlib.md5(l[2].encode('utf-8')).hexdigest()))

Answer 6

I don't think you can decrypt it but what you can do is maybe take the range of guessed passwords for example in a for loop and put all of them "{password: hashed password" then check the hash and maybe you'll get it

so let's say you wanna crack a password that is in a CSV file and is between 0000-9999

the input csv file would be like :

name, hashed password

first we'll import csv and hashlib

import hashlib
import csv

now lets write a function that takes the hashed csv file and output csv file as arguments we'll make an empty string and an empty dict

def decryptor(input_file_name,output_file_name):
    # makes hashes
    clear_text = ""
    mydict = {}

now lets make a for loop in range of 0 and 9999 and we will encypt every number in that range

    for i in range(0, 10000):
        i = str(i).encode('utf-8') 
        encrypted = hashlib.sha256(i).hexdigest()
        mydict[i] = encrypted

now we'll just write them in csv file

    with open(input_file_name, 'r') as hash_file:
        # read's from csv file
        reader = csv.reader(hash_file)
        hash_dict = {}
        # reades every line of csv file
        for row in reader:
                hash_dict[row[0]] = row[1]

now we just need to check the hash we wanna decrypt with the hashes we already have and we'll get the unhashed password

    check_hash = []
    for i in list(mydict):
        text = "%s" % (mydict[i])
        check_hash.append(mydict[i])
    for i in list(hash_dict):
        if hash_dict[i] in check_hash:
            hashes = list(mydict.keys())[list(mydict.values()).index(hash_dict[i])]
            names = list(hash_dict.keys())[list(hash_dict.values()).index(hash_dict[i])],
            text = "%s,%s\n" % (names[0], hashes.decode('utf-8'))
            clear_text += text

now we write the out put to the output csv file

    with open(output_file_name, 'w') as passwords:
        passwords.write(clear_text)

and we'll just call the function

decryptor(<INPUT CSV>, <OUTPUT CSV NAME>)

This is my idea for you of cource you can't use this this is an idea hope it'll help :)