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76 lines
2.3 KiB
76 lines
2.3 KiB
3 years ago
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# pkcs7
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[](https://travis-ci.org/brightcove/pkcs7)
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[](https://greenkeeper.io/)
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[](http://slack.videojs.com)
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[](https://nodei.co/npm/pkcs7/)
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> Add and remove pkcs7-style padding.
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<!-- START doctoc generated TOC please keep comment here to allow auto update -->
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<!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
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**Table of Contents** *generated with [DocToc](https://github.com/thlorenz/doctoc)*
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- [Getting Started](#getting-started)
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- [Documentation](#documentation)
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- [Examples](#examples)
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- [Contributing](#contributing)
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- [License](#license)
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<!-- END doctoc generated TOC please keep comment here to allow auto update -->
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## Getting Started
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Install the module with: `npm install pkcs7`
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```js
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var pkcs7 = require('pkcs7'), encrypted;
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// pad a buffer!
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enctcrypted = encrypt(pkcs7.pad(buffer));
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// later, you can unpad it:
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console.log('the secret is out! ' + pkcs7.unpad(decrypt(encrypted)));
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```
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Install with cli command
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```sh
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$ npm install -g pkcs7
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$ pkcs7 --help
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$ pkcs7 --version
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```
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## Documentation
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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:
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01 -- if lth mod k = k-1
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02 02 -- if lth mod k = k-2
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.
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.
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.
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k k ... k k -- if lth mod k = 0
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`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](http://tools.ietf.org/html/rfc5652).
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## Examples
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You can run pkcs7 from the command line:
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```shell
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# pad a string generated by echo and the hex dump the result
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echo -n "0123456789AB" | pkcs7 | xxd
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```
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## Contributing
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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](http://gruntjs.com).
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## License
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Copyright (c) 2014 Brightcove
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Licensed under the Apache-2 license.
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