Some Secure Password Theory in Java

Painting Data Matrix in Java Some Secure Password Theory
722 Some Secure Password Theory
Draw Data Matrix In Java
Using Barcode drawer for Java Control to generate, create Data Matrix image in Java applications.
The basic idea of encrypted passwords is simple: rather than storing a raw password in the database (known as cleartext ), we store a string generated using a cryptographic hash function, which is essentially irreversible, so that even an attacker in possession of the hashed password will be unable to infer the original To verify that a submitted password matches the user s password, we first encrypt the submitted string and then compare the hashes Let s drop into a console session to see how this works:
Print Barcode In Java
Using Barcode drawer for Java Control to generate, create bar code image in Java applications.
Secure Passwords
Barcode Recognizer In Java
Using Barcode decoder for Java Control to read, scan read, scan image in Java applications.
$ rails console >> require 'digest' >> def secure_hash(string) >> Digest::SHA2hexdigest(string) >> end => nil >> password = "secret" => "secret" >> encrypted_password = secure_hash(password) => "2bb80d537b1da3e38bd30361aa855686bde0eacd7162fef6a25fe97bf527a25b" >> submitted_password = "secret" => "secret" >> encrypted_password == secure_hash(submitted_password) => true
Encoding Data Matrix 2d Barcode In C#
Using Barcode creator for Visual Studio .NET Control to generate, create Data Matrix image in .NET framework applications.
Here we ve defined a function called secure_hash that uses a cryptographic hash function called SHA2, part of the SHA family of hash functions, which we include into Ruby through the digest library7 It s not important to know exactly how these hash functions work; for our purposes what s important is that they are one-way: there is no computationally tractable way to discover that
Encoding Data Matrix 2d Barcode In .NET
Using Barcode encoder for ASP.NET Control to generate, create ECC200 image in ASP.NET applications.
2bb80d537b1da3e38bd30361aa855686bde0eacd7162fef6a25fe97bf527a25b
Data Matrix Creator In Visual Studio .NET
Using Barcode drawer for VS .NET Control to generate, create Data Matrix image in .NET applications.
is the SHA2 hash of the string "secret" If you think about it, though, we still have a problem: if an attacker ever got hold of the hashed passwords, he would still have a chance at discovering the originals For example, he could guess that we used SHA2, and so write a program to compare a given hash to the hashed values of potential passwords:
DataMatrix Generation In Visual Basic .NET
Using Barcode drawer for VS .NET Control to generate, create DataMatrix image in Visual Studio .NET applications.
>> >> => >> => >> => hash = "2bb80d537b1da3e38bd30361aa855686bde0eacd7162fef6a25fe97bf527a25b" secure_hash("secede") == hash false secure_hash("second") == hash false secure_hash("secret") == hash true
Bar Code Creation In Java
Using Barcode creator for Java Control to generate, create barcode image in Java applications.
7 In my setup, the require digest line is unnecessary, but several readers have reported getting a NameError exception if they don t include it explicitly It does no harm in any case, so I ve included the explicit require just to be safe
Data Matrix Maker In Java
Using Barcode drawer for Java Control to generate, create DataMatrix image in Java applications.
7: Modeling and Viewing Users, Part II
Create Code-128 In Java
Using Barcode encoder for Java Control to generate, create Code 128B image in Java applications.
So our attacker has a match bad news for any users with password "secret" This technique is known as a rainbow attack To foil a potential rainbow attack, we can use a salt, which is a different unique string for each user8 One common way to (nearly) ensure uniqueness is to hash the current time (in UTC to be time-zone independent) along with the password, so that two users will have the same salt only if they are created at exactly the same time and have the same password Let s see how this works using the secure_hash function defined in the console above:
Draw EAN 128 In Java
Using Barcode creation for Java Control to generate, create GTIN - 128 image in Java applications.
>> => >> => >> => >> => Timenowutc Fri Jan 29 18:11:27 UTC 2010 password = "secret" "secret" salt = secure_hash("#{Timenowutc}--#{password}") "d1a3eb8c9aab32ec19cfda810d2ab351873b5dca4e16e7f57b3c1932113314c8" encrypted_password = secure_hash("#{salt}--#{password}") "69a98a49b7fd103058639be84fb88c19c998c8ad3639cfc5deb458018561c847"
Code 39 Extended Encoder In Java
Using Barcode creator for Java Control to generate, create Code 39 Full ASCII image in Java applications.
In the last line, we ve hashed the salt with the password, yielding an encrypted password that is virtually impossible to crack (For clarity, arguments to hashing functions are often separated with --)
Making 2 Of 5 Interleaved In Java
Using Barcode generator for Java Control to generate, create ANSI/AIM ITF 25 image in Java applications.
723 Implementing has_password
EAN13 Decoder In VS .NET
Using Barcode recognizer for Visual Studio .NET Control to read, scan read, scan image in Visual Studio .NET applications.
Having finished with the theory, we re now ready for the implementation Let s look ahead a little to see where we re going Each user object knows its own encrypted password, so to check for a match with a submitted password we can define has_password as follows:
UCC - 12 Creation In .NET
Using Barcode printer for ASP.NET Control to generate, create EAN / UCC - 13 image in ASP.NET applications.
def has_password (submitted_password) encrypted_password == encrypt(submitted_password) end
Generate Bar Code In .NET
Using Barcode printer for ASP.NET Control to generate, create bar code image in ASP.NET applications.
As long as we encrypt the submitted password using the same salt used to encrypt the original password, this function will be true if and only if the submitted password matches
Paint USS Code 128 In Visual C#
Using Barcode generation for Visual Studio .NET Control to generate, create Code 128 Code Set C image in .NET framework applications.
8 Technically, rainbow attacks could still succeed, but using a salted hash makes them computationally unfeasible
Paint Code 128 Code Set C In .NET Framework
Using Barcode creator for ASP.NET Control to generate, create Code-128 image in ASP.NET applications.
Secure Passwords
Paint Barcode In C#.NET
Using Barcode maker for VS .NET Control to generate, create bar code image in Visual Studio .NET applications.
Since comparing a user password with a submitted password will involve encrypting the submitted password with the salt, we need to store the salt somewhere, so the first step is to add a salt column to the users table:
Recognize Data Matrix In VS .NET
Using Barcode reader for .NET framework Control to read, scan read, scan image in .NET applications.