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添加宜春 天水 宣化
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# pkcs7 [](http://travis-ci.org/brightcove/pkcs7)
> Add and remove pkcs7-style padding.
## Getting Started
Install the module with: `npm install pkcs7`
```js
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
```sh
$ 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](http://tools.ietf.org/html/rfc5652).
## Examples
You can run pkcs7 from the command line:
```shell
# 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](http://gruntjs.com).
## License
Copyright (c) 2014 Brightcove
Licensed under the Apache-2 license.
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