gendsa.1s

openssl gendsa [options] dsa_parameters_file

Where dsa_parameters_file is a path to a file containing the DSA parameters (P, Q, G) to be used for key generation.

dsa_parameters_file
    Required argument. Specifies the path to a file containing the DSA parameters (P, Q, G) from which the private key will be derived.

-out filename
    Specifies the output file for the generated DSA key. If this option is not used, the key is written to standard output (stdout).

-rand file(s)
    Specifies one or more files (colon-separated) to read random data from, used to seed the Pseudo-Random Number Generator (PRNG).

-engine id
    Specifies a cryptographic engine to be used, overriding the default engine.

-passout arg
    Specifies the source for the output file's pass phrase, used if the private key is encrypted.

-aes128 | -aes192 | -aes256 | -camellia128 | -camellia192 | -camellia256 | -des | -des3 | -idea | -seed
    Encryption options. These flags encrypt the generated private key using the specified symmetric cipher (e.g., AES, DES3). A passphrase will be prompted or read via -passout.

openssl gendsa is a subcommand of the openssl command-line tool, used for generating a new DSA (Digital Signature Algorithm) private key. Unlike RSA key generation, gendsa does not create the DSA parameters (P, Q, G) itself. Instead, it requires these parameters to be provided in an input file, typically generated beforehand using commands like openssl dsaparam.

Once provided with valid parameters, gendsa generates the private component (X) of the DSA key pair and calculates the corresponding public component (Y). The generated private key can be optionally encrypted with a passphrase using various symmetric encryption algorithms. This command is a fundamental part of establishing secure communications and digital signing capabilities in systems relying on DSA cryptography, providing the essential private key required for these operations.

• The gendsa command itself does not generate DSA parameters (P, Q, G). These must be pre-generated, typically using openssl dsaparam, and provided as an input file. Without valid parameters, the command will fail.
• The security of the generated DSA key heavily relies on the quality of the DSA parameters provided and the randomness used by the PRNG. Ensure parameters are strong and the PRNG is sufficiently seeded, especially for production environments.

The Digital Signature Algorithm (DSA) requires a set of global parameters (P, Q, G) to be established first. These parameters define the cryptographic group in which the key operations occur. gendsa uses these parameters to generate the unique private (X) and public (Y) components of an individual DSA key pair.

When a private key is generated, it's often encrypted with a passphrase to protect it from unauthorized access. gendsa supports various symmetric encryption algorithms (e.g., AES, DES3) for this purpose, ensuring that even if the key file is compromised, its contents remain unreadable without the correct passphrase.

The gendsa subcommand has been a part of the OpenSSL toolkit for a long time, evolving with the OpenSSL project itself. Its development is tied to the general support for DSA cryptography within OpenSSL, providing a standard utility for generating the private component of DSA key pairs once the domain parameters are established. As a core cryptographic tool, its functionality has remained relatively stable, with updates primarily focusing on security enhancements, performance, and integration with newer OpenSSL features like engines and various symmetric encryption algorithms for key protection.

openssl(1), openssl dsaparam(1), openssl dsa(1), openssl genrsa(1)