- NAME
- SYNOPSIS
- DESCRIPTION
- OPTIONS
- NOTES
- SEE ALSO
- HISTORY
- COPYRIGHT

# NAME

openssl-ech - ECH key generation

# SYNOPSIS

openssl ech [-help] [-verbose] [-in files] [-out file] [-public_name name] [-max_name_len len] [-suite suite_str] [-ech_version version] [-select number] [-text]

# DESCRIPTION

The openssl-ech(1) command generates Encrypted Client Hello (ECH) key pairs in the ECHConfig PEM file format as specified in https://datatracker.ietf.org/doc/rfc9934.

That format consists of an optional private key in PKCS#8 format and a base64 encoded ECHConfigList containing an entry with a matching public value (and possibly other entries as well).

# OPTIONS

The following options are supported:

-help

  Print out a usage message.

-verbose

  Print more verbosely.

-in

  Provide an input ECH PEM file for printing or merging. Up to five input files can be provided via use of multiple in arguments.

-out file

  Name of output ECHConfig PEM file. If a new key pair was generated the output file will contain the private key and encoded ECHConfigList. If one or more input files was provided the output file will contain a set of ECHConfigList values with public keys from the inputs, and no private key(s).

-text

  Provide human-readable text output.

-public_name name

  The DNS name to use in the "public_name" field of the ECHConfig.

-max_name_len num

  Maximum name length field value to use in the ECHConfig.

-suite str

  HPKE suite to use in the ECHConfig.

-ech_version version

  The ECH version to use in the ECHConfig. Only 0xfe0d is supported in this version.

-select number

  Select the N-th ECHConfig/public key from the set of input ECH PEM files and output that.

# NOTES

Ciphersuites are specified using a comma-separated list of IANA-registered codes/numbers e.g. "-c 0x20,1,3" or a comma-separated list of strings from: - KEMs: p256, p384, p521, x25519, x448 - KDFs: hkdf-sha256, hkdf-sha384, hkdf-sha512 - AEADs: aes128gcm, aes256gcm, chachapoly1305

For example the default is: x25519, hkdf-sha256, aes128gcm See OSSL_HPKE_CTX_new(3) for details.

# SEE ALSO

openssl(1), openssl-s_client(1), openssl-s_server(1), SSL_set1_echstore(3)

# HISTORY

This functionality described here was added in OpenSSL 4.0.

# COPYRIGHT

Copyright 2024-2026 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at https://www.openssl.org/source/license.html.