gendsa - Unix, Linux Command


gendsa - generate a DSA private key from a set of parameters


openssl gendsa [-out filename] [-des] [-des3] [-idea] [-rand file(s)] [-engine id] [paramfile]


The gendsa command generates a DSA private key from a DSA parameter file (which will be typically generated by the openssl dsaparam command).


-des|-des3|-idea These options encrypt the private key with the DES, triple DES, or the IDEA ciphers respectively before outputting it. A pass phrase is prompted for. If none of these options is specified no encryption is used.
-rand file(s) a file or files containing random data used to seed the random number generator, or an EGD socket (see RAND_egd(3)). Multiple files can be specified separated by a OS-dependent character. The separator is ; for MS-Windows, , for OpenVMS, and : for all others.
-engine id specifying an engine (by it’s unique id string) will cause req to attempt to obtain a functional reference to the specified engine, thus initialising it if needed. The engine will then be set as the default for all available algorithms.
paramfile This option specifies the DSA parameter file to use. The parameters in this file determine the size of the private key. DSA parameters can be generated and examined using the openssl dsaparam command.


DSA key generation is little more than random number generation so it is much quicker that RSA key generation for example.


Below example shows creation of DSA key pair and certificate

Step 1 - Create DSA parameter file

This parameter file will instruct OpenSSL to create 2048-bit key.
$ openssl dsaparam -out dsaparam.pem 2048

Step 2 - Generate private key

If the encryption option -des|-des3|-idea is specified the the command will prompt for pass phrase.
$ openssl gendsa -des -out dsaprivkey.pem dsaparam.pem
Generating DSA key, 2048 bits
Enter PEM pass phrase:
Verifying - Enter PEM pass phrase:

Step 3 - Extract the public key into a DER format

$ openssl dsa -in dsaprivkey.pem -outform DER -pubout -out dsapubkey.der
read DSA key
Enter pass phrase for dsaprivkey.pem:
writing DSA key

Step 4 - Converts the private key into the pkcs8 and DER format

$ openssl pkcs8 -topk8 -inform PEM -outform DER -in dsaprivkey.pem -out dsaprivkey.der -nocrypt
Enter pass phrase for dsaprivkey.pem:

Step 5 - Create Certificate

$ openssl req -new -x509 -key dsaprivkey.pem -out dsacert.pem
Enter pass phrase for dsaprivkey.pem:

After answering few questions the certificate will be generated.
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