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dsaparam Command in Linux
The Linux dsaparam command creates and manipulates the DSA parameter file. The Digital Signature Algorithm (DSA) parameter file contains the parameters used to generate and verify digital signatures. It is also used to create the private and public DSA keys.
The dsaparam command is a part of the openssl command line utility that uses cryptographic functions to implement the SSL and TLS protocols.
Table of Contents
Here is a comprehensive guide to the options available with the dsaparam command −
- Prerequisites to Use the dsaparam Command
- Syntax of dsaparam Command
- dsaparam Command Options
- Using dsaparam Command in Linux
Prerequisites to Use the dsaparam Command
The dsaparam command is a part of OpenSSL, therefore, OpenSSL must be installed and configured on Linux. To check whether it is installed, use the following command −
openssl version -a
If the output shows a version, then it means the OpenSSL is installed, otherwise, follow the instructions below to install it.
To install OpenSSL on Ubuntu, its variants, Debian, and Debian-based distributions, use the command given below −
sudo apt install openssl
To install OpenSSL on RHEL, and CentOS, use the following command −
sudo yum install openssl
Syntax of dsaparam Command
The syntax of Linux openssl dsaparam command is as follows −
openssl dsaparam [options]
The [options] field is used to specify options to generate and modify the parameter file.
dsaparam Command Options
The options used with the openssl dsaparam command are listed in the following table −
| Options | Description |
|---|---|
| -inform DER | PEM | It is used to specify the input file format (.pem or .der) |
| -outform DER | PEM | It is used to specify the output file format (.pem or .der) |
| -in filename | It is used to specify the input file name read parameters from |
| -out filename | It is used to specify the output file name to write parameters to |
| -noout | It suppresses the output of an encoded key |
| -text | It displays the public and private key components and parameters in a human-readable form |
| -C | This option converts parameters in C code (parameters can be loaded using dsaXXX() function) |
| -genkey | It is used to generate DSA using specified parameters |
| -rand file(s) | It is used to specify a file with random data to seed random number generator |
| -numbits | It is used to specify the size of the parameter to be generated (e.g., 1024, 2048, 3072) |
| -engine id | It is used to specify the engine through a string of id |
Using dsaparam Command in Linux
This section demonstrates the usage of the Linux openssl dsaparam command.
Generating a DSA Parameter File
To generate the DSA parameter file with a length of 2048, use the openssl dsaparam command, and write the output to a file using the -out option −
openssl dsaparam -out dsaparameter.pem 2048
A parameter file will be generated in the current working directory. The parameter can also be generated to standard output using −
openssl dsaparam 2048
The parameter data in a .pem file is enclosed in the header -----BEGIN DSA PARAMETERS----- and footer -----END DSA PARAMETERS-----.
Displaying the Parameters of Parameter File
To display all the parameters of the parameter file, use -text option −
openssl dsaparam -in dsaparameter.pem -text -noout
The dsaparameter.pem is the parameter file, while -text displays all the parameters. The -noout option is used to skip the encoded key from the output.
The parameter file contains the following components −
| Component | Description |
|---|---|
| P | A prime number typically in 1024, 2048, and 3072 bits in length |
| Q | A prime number with a factor P-1 typically in 160, 256 bits in length |
| G | A number that generates the subgroup of order Q modulo P: computed by G=H^(P-1)/Q where 1 < H < P-1 |
Generating a Private Key using the Parameter File
The parameter file can also be used to create a private key using the -genkey option −
openssl dsaparam -in dsaparameter.pem -genkey -out privatekey.pem
Converting the Parameter File Format
To convert the format of a parameter file, use the -outform option −
openssl dsaparam -in dsaparameter.pem -outform DER -out dsaparameter.der
Conclusion
The dsaparam command is used to generate and modify a DSA parameter file. It is a component of the openssl command line utility. Therefore, to use it in Linux, OpenSSL must be installed.
The dsaparam is primarily used to generate parameter files, which are further used to create DSA private and public keys.
In this tutorial, we explained the openssl dsaparam command, its syntax, options, and usage in Linux.