Error in crypto deciphering

Question

Why does the following code throw up a DecipherFinal error in crypto -

  var crypto = require('crypto');
  c=new Date;
  x= (c.getTime()+"."+c.getMilliseconds()).toString()+".uIn";
  key = 'sevsolut'
        , plaintext = x
        , cipher = crypto.createCipher('aes-256-cbc', key)
        , decipher = crypto.createDecipher('aes-256-cbc', key);
  cipher.update(plaintext, 'utf8', 'base64');
  var encryptedPassword = cipher.final('base64')

  decipher.update(encryptedPassword, 'base64', 'utf8');
  var decryptedPassword = decipher.final('utf8');

  console.log('encrypted :', encryptedPassword);
  console.log('decrypted :', decryptedPassword);

@pfried parentheses are optional when instantiating objects in JS, as long as you don't need to pass arguments. — robertklep, Apr 04 '13 at 08:53
@robertklep Everyday something new :D But i think for better reading it would be helpful — pfried, Apr 04 '13 at 09:36
@Mchl its prototype code..its not for encrypting passwords... — digster, Apr 04 '13 at 10:20

score 2 · Accepted Answer · answered Apr 04 '13 at 09:03

2

You need to take the output from update:

var crypto = require('crypto');
c=new Date();
x= (c.getTime()+"."+c.getMilliseconds()).toString()+".uIn";
key = "sevsolut"
      , plaintext = x
      , cipher = crypto.createCipher('aes-256-cbc', key)
      , decipher = crypto.createDecipher('aes-256-cbc', key);
var encryptedPassword = cipher.update(plaintext, 'utf8', 'base64');
encryptedPassword += cipher.final('base64')

var decryptedPassword = decipher.update(encryptedPassword, 'base64', 'utf8');
decryptedPassword += decipher.final('utf8');

console.log('encrypted :', encryptedPassword);
console.log('decrypted :', decryptedPassword);

answered Apr 04 '13 at 09:03

laktak

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@chris..it worked perfectly :) ..however would like to point out one thing.. the code in question seems to work perfectly for strings of certain length(try it with a small simple string)..only when it goes above certain length is I guess when we have to employ adding the update step..can u shed some light on it? – digster Apr 04 '13 at 10:38
Not sure what you mean. Update returns the enciphered contents, and can be called many times with new data as it is streamed - final returns any remaining enciphered contents. – laktak Apr 04 '13 at 11:03
i meant say use x= "simple" as the plaintext input..then the code in the question works perfectly..however if x= some big string..then the code in the question fails and we have to proceed according to your example.... – digster Apr 04 '13 at 12:42
1

Encryption is done block by block. If you don't put in enough for a block the update function won't return anything. – laktak Apr 04 '13 at 18:14

Error in crypto deciphering

1 Answers1