# Crypt4GH utility
## Introduction
Bob wants to send a message to Alice, containing sensitive data. Bob uses [Crypt4GH, the Global Alliance approved secure method for sharing human genetic data](https://www.ga4gh.org/news/crypt4gh-a-secure-method-for-sharing-human-genetic-data/)
crypt4gh, a Rust tool to encrypt, decrypt or re-encrypt files, according to the [GA4GH encryption file format](http://samtools.github.io/hts-specs/crypt4gh.pdf). [](https://www.ga4gh.org/news/crypt4gh-a-secure-method-for-sharing-human-genetic-data/)
## Basic example
Alice and Bob generate both a pair of public/private keys.
```sh
crypt4gh keygen --sk alice.sec --pk alice.pub
crypt4gh keygen --sk bob.sec --pk bob.pub
```
Bob encrypts a file for Alice:
```sh
crypt4gh encrypt --sk bob.sec --recipient_pk alice.pub < file > file.c4gh
```
Alice decrypts the encrypted file:
```sh
crypt4gh decrypt --sk alice.sec < file.c4gh
```