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README.md

pkcs7

Add and remove pkcs7-style padding.

Getting Started

Install the module with: npm install pkcs7

var pkcs7 = require('pkcs7'), encrypted;
// pad a buffer!
enctcrypted = encrypt(pkcs7.pad(buffer));

// later, you can unpad it:
console.log('the secret is out! ' + pkcs7.unpad(decrypt(encrypted)));

Install with cli command

$ npm install -g pkcs7
$ pkcs7 --help
$ pkcs7 --version

Documentation

PKCS#7 padding a really simple transformation some crytographic algorithms use to ensure the number of input bytes is a multiple of some constant. Here's how it works:

         01 -- if lth mod k = k-1
      02 02 -- if lth mod k = k-2
          .
          .
          .
k k ... k k -- if lth mod k = 0

k is the constant value the encryption algorithm wants your input to be a multiple of. This project assumes k is always sixteen. Not much to it, right? If reading specs is your thing, check out RFC 5652.

Examples

You can run pkcs7 from the command line:

# pad a string generated by echo and the hex dump the result
echo -n "0123456789AB" | pkcs7 | xxd

Contributing

In lieu of a formal styleguide, take care to maintain the existing coding style. Add unit tests for any new or changed functionality. Lint and test your code using Grunt.