How to decrypt hash stored by bcrypt

Question

I have this script that encrypts a password but I don t know how to reverse it and decrypt it  This may be a very simple answer but I don t understand how to do it      usr bin perl use Crypt  Eksblowfish  Bcrypt  use Crypt  Random    password    bigtest    encrypted   encrypt password  password   print   password is encrypted as  encrypted n    print  Yes the password is  password n  if check password  password   encrypted   print  No the password is not smalltest n  if  check password  smalltest    encrypted      Encrypt a password  sub encrypt password       my  password   shift         Generate a salt if one is not passed     my  salt   shift    salt            Set the cost to 8 and append a NUL     my  settings     2a 08    salt         Encrypt it     return Crypt  Eksblowfish  Bcrypt  bcrypt  password   settings        Check if the passwords match sub check password       my   plain password   hashed password               Regex to extract the salt     if   hashed password    m    2a   d 2     A-Za-z0-9      22               return encrypt password  plain password   1  eq  hashed password        else           return 0             Return a random salt sub salt       return Crypt  Eksblowfish  Bcrypt  en base64 Crypt  Random  makerandom octet Length  gt 16

User · Answer

You can use the password verify function with the PHP  It verifies that a password matches with the hash password verify   string  password   string  hash     bool more details  https   www php net manual en function password-verify php

User · Answer

Maybe you search this    For example in my case I use Symfony 4 4  PHP   If you want to update User  you need to insert the User password  encrypted and test with the current Password not encrypted to verify  if it s the same User    For example    public function updateUser Request  req                    entityManager    this- gt getDoctrine  - gt getManager              repository    entityManager- gt getRepository User  class             user    repository- gt find  req- gt get id        get User from your DB           if  user    null               throw   this- gt createNotFoundException  User don t exist      user                        password old encrypted    user- gt getPassword     in your DB is always encrypted            passwordToUpdate    req- gt get  password       not encrypted yet from request             passwordToUpdateEncrypted   password hash  passwordToUpdate   PASSWORD DEFAULT                          VERIFY IF IT S THE SAME PASSWORD           isPass   password verify  passwordToUpdateEncrypted    password old encrypted              if  isPass     false      failure             throw   this- gt createNotFoundException  Your password it s not verify   null                       return  isPass       true   it s the same password

User · Answer

You can t decrypt but you can BRUTEFORCE IT    I E  iterate a password list and check if one of them match with stored hash  script from github  https   github com BREAKTEAM Debcrypt

User · Answer

To answer the original posters question     to  decrypt  the password  you have to do what a password cracker would do     In other words  you d run a program to read from a large list of potential passwords  a password dictionary  and you d hash each one using bcrypt and the salt and complexity from the password you re trying to decipher   If you re lucky you ll find a match  but if the password is a strong one then you likely won t find a match     Bcrypt has the added security characteristic of being a slow hash   If your password had been hashed with md5  terrible choice  then you d be able to check billions of passwords per second  but since it s hashed using bcrypt you will be able to check far fewer per second     The fact that bcrypt is slow to hash and salted is what makes it a good choice for password storage even today   That being said I believe NIST recommends the PBKDF2 for password hashing

User · Answer

You simply can t   bcrypt uses salting  of different rounds  I use 10 usually   bcrypt hash req body password 10 function error response       This 10 is salting random string into your password

User · Answer

You re HASHING  not ENCRYPTING   What s the difference   The difference is that hashing is a one way function  where encryption is a two-way function   So  how do you ascertain that the password is right   Therefore  when a user submits a password  you don t decrypt your stored hash  instead you perform the same bcrypt operation on the user input and compare the hashes  If they re identical  you accept the authentication   Should you hash or encrypt passwords   What you re doing now -- hashing the passwords -- is correct  If you were to simply encrypt passwords  a breach of security of your application could allow a malicious user to trivially learn all user passwords  If you hash  or better  salt and hash  passwords  the user needs to crack passwords  which is computationally expensive on bcrypt  to gain that knowledge   As your users probably use their passwords in more than one place  this will help to protect them

[perl] How to decrypt hash stored by bcrypt

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