javascript - CryptoJS how to generate a key every time? - Stack Overflow

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Let assume that I have an Phonegap mobile app, and I want to store some user data(username/pass_hash) in local indexed db for providing login to app in offline. I want to encrypt that data of course, and my app already use CryptoJS. As I understood, first I need to generate encryption_key by password using PBKDF2, and then just encrypt CryptoJS.AES. Example code:

function generateKey(p){
var salt = CryptoJS.lib.WordArray.random(128/8);
return CryptoJS.PBKDF2(p, salt, { keySize: 512/32, iterations: 1000 });     
}

var pass = "test1"; 
var iv  = CryptoJS.lib.WordArray.random(16);
key512Bits1000Iterations = generateKey(pass);
var encrypted = CryptoJS.AES.encrypt("Message", key512Bits1000Iterations, { iv: iv });
var decrypted = CryptoJS.AES.decrypt(encrypted, key512Bits1000Iterations, { iv: iv });

//decrypting with another key step
key512Bits1000Iterations2 = generateKey(pass);
var decrypted2 = CryptoJS.AES.decrypt(encrypted, key512Bits1000Iterations2, { iv: iv });
console.log("decrypted " + decrypted.toString(CryptoJS.enc.Utf8));
console.log("decrypted2 " + decrypted2.toString(CryptoJS.enc.Utf8));

Dynamic salt and iv are used. But when I second time generate key for decryption by same password I'm getting wrong result.(decrypted2 is empty) So I want to ask, what I should store between encryption sessions, salt and iv to ?(but as I understood it should be dynamic ) Thanks!

Let assume that I have an Phonegap mobile app, and I want to store some user data(username/pass_hash) in local indexed db for providing login to app in offline. I want to encrypt that data of course, and my app already use CryptoJS. As I understood, first I need to generate encryption_key by password using PBKDF2, and then just encrypt CryptoJS.AES. Example code:

function generateKey(p){
var salt = CryptoJS.lib.WordArray.random(128/8);
return CryptoJS.PBKDF2(p, salt, { keySize: 512/32, iterations: 1000 });     
}

var pass = "test1"; 
var iv  = CryptoJS.lib.WordArray.random(16);
key512Bits1000Iterations = generateKey(pass);
var encrypted = CryptoJS.AES.encrypt("Message", key512Bits1000Iterations, { iv: iv });
var decrypted = CryptoJS.AES.decrypt(encrypted, key512Bits1000Iterations, { iv: iv });

//decrypting with another key step
key512Bits1000Iterations2 = generateKey(pass);
var decrypted2 = CryptoJS.AES.decrypt(encrypted, key512Bits1000Iterations2, { iv: iv });
console.log("decrypted " + decrypted.toString(CryptoJS.enc.Utf8));
console.log("decrypted2 " + decrypted2.toString(CryptoJS.enc.Utf8));

Dynamic salt and iv are used. But when I second time generate key for decryption by same password I'm getting wrong result.(decrypted2 is empty) So I want to ask, what I should store between encryption sessions, salt and iv to ?(but as I understood it should be dynamic ) Thanks!

• javascript
• cordova
• encryption
• cryptojs

Share Improve this question Follow asked Nov 15, 2016 at 9:22 MaximMaxim 1111 gold badge11 silver badge22 bronze badges 2

• If you're using salt for encryption, than you'd need to use the very same salt value to decrypt the message. – Eduard Malakhov Commented Nov 15, 2016 at 9:40
• 1 Thanks! I also found a good article crackstation/hashing-security.htm may be useful someone. – Maxim Commented Nov 15, 2016 at 10:44

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1 Answer 1

Sorted by: Reset to default 3

You are generating a new salt in generateKey(...). This makes PBKDF2 derived a new key.

function generateKey(p){
    var salt = CryptoJS.lib.WordArray.random(128/8);
    return CryptoJS.PBKDF2(p, salt, { keySize: 512/32, iterations: 1000 });     
}

You would need to store the salt and iv between sessions. These two values don't need to be secret.

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