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Crypt4GH Encryption Utility

crypt4ghis a Python tool to encrypt, decrypt or re-encrypt files, according to the GA4GH encryption file format.


Python 3.6+ required to use the crypt4gh encryption utility.

Install it from PyPI:

pip install crypt4gh

or if you prefer the latest sources from Github:

git clone
pip install -r crypt4gh/requirements.txt
pip install ./crypt4gh


pip install git+


The usual -h flag shows you the different options that the tool accepts.

$ crypt4gh -h

Utility for the cryptographic GA4GH standard, reading from stdin and outputting to stdout.

   {PROG} [-hv] [--log <file>] encrypt [--sk <path>] --recipient_pk <path> [--recipient_pk <path>]... [--range <start-end>]
   {PROG} [-hv] [--log <file>] decrypt [--sk <path>] [--sender_pk <path>] [--range <start-end>]
   {PROG} [-hv] [--log <file>] rearrange [--sk <path>] --range <start-end>
   {PROG} [-hv] [--log <file>] reencrypt [--sk <path>] --recipient_pk <path> [--recipient_pk <path>]... [--trim]

   -h, --help             Prints this help and exit
   -v, --version          Prints the version and exits
   --log <file>           Path to the logger file (in YML format)
   --sk <keyfile>         Curve25519-based Private key.
                          When encrypting, if neither the private key nor C4GH_SECRET_KEY are specified, we generate a new key 
   --recipient_pk <path>  Recipient's Curve25519-based Public key
   --sender_pk <path>     Peer's Curve25519-based Public key to verify provenance (akin to signature)
   --range <start-end>    Byte-range either as  <start-end> or just <start> (Start included, End excluded)
   -t, --trim             Keep only header packets that you can decrypt

Environment variables:
   C4GH_LOG         If defined, it will be used as the default logger
   C4GH_SECRET_KEY  If defined, it will be used as the default secret key (ie --sk ${C4GH_SECRET_KEY})


Alice and Bob generate both a pair of public/private keys.

$ crypt4gh-keygen --sk alice.sec --pk
$ crypt4gh-keygen --sk bob.sec --pk

Bob encrypts a file for Alice:

$ crypt4gh encrypt --sk bob.sec --recipient_pk < file > file.c4gh

Alice decrypts the encrypted file:

$ crypt4gh decrypt --sk alice.sec < file.c4gh


File Format

Refer to the specifications or this documentation.

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