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Commands Reference, Volume 2

dnssec-keygen Command


DNSSEC key generation tool.


dnssec-keygen [ -a algorithm ] [ -b keysize ] [ -n nametype ] [-c class ] [ -e ] [-g generator ] [ -h ] [ -p protocol ] [ -r randomdev ] [ -s strength ] [ -t type ] [ -v level ] [ name ]


The dnssec-keygen command generates keys for DNSSEC (Secure DNS), as defined in RFC 2535. It can also generate keys for use with TSIG (Transaction Signatures), as defined in RFC 2845.


-a algorithm Selects the cryptographic algorithm. The value of algorithm must be one of RSAMD5 or RSA, DSA, DH (Diffie Hellman), or HMAC-MD5. These values are case insensitive. Note that for DNSSEC, DSA is a mandatory to implement algorithm, and RSA is recommended. For TSIG, HMAC-MD5 is mandatory.
-b keysize Specifies the number of bits in the key. The choice of key size depends on the algorithm used. RSA keys must be between 512 and 2048 bits. Diffie Hellman keys must be between 128 and 4096 bits. DSA keys must be between 512 and 1024 bits and an exact multiple of 64. HMAC-MD5 keys must be between 1 and 512 bits.
-n nametype Specifies the owner type of the key. The value of nametype must either be ZONE (for a DNSSEC zone key), HOST or ENTITY (for a key associated with a host), or USER (for a key associated with a user). These values are case insensitive.
-c class Indicates that the DNS record containing the key should have the specified class. If not specified, class IN is used.
-e If generating an RSA key, use a large exponent.
-g generator If generating a Diffie Hellman key, use this generator. Allowed values are 2 and 5. If no generator is specified, a known prime from RFC 2539 will be used if possible; otherwise the default is 2.
-h Prints a short summary of the options and arguments to dnssec-keygen.
-p protocol Sets the protocol value for the generated key. The protocol is a number between 0 and 255. The default is 2 (email) for keys of type USER and 3 (DNSSEC) for all other key types. Other possible values for this argument are listed in RFC 2535 and its successors.
-r randomdev Specifies the source of randomness. If the operating system does not provide a /dev/random or equivalent device, the default source of randomness is keyboard input. randomdev specifies the name of a character device or file containing random data to be used instead of the default. The special value keyboard indicates that keyboard input should be used.
-s strength Specifies the strength value of the key. The strength is a number between 0 and 15, and currently has no defined purpose in DNSSEC.
-t type Indicates the use of the key. type must be one of AUTHCONF, NOAUTHCONF, NOAUTH, or NOCONF. The default is AUTHCONF. AUTH refers to the ability to authenticate data, and CONF the ability to encrypt data.
-v level Sets the debugging level.

Generated Keys

When dnssec-keygen completes successfully, it prints a string of the form Knnnn.+aaa+iiiii to the standard output. This is an identification string for the key it has generated. These strings can be used as arguments to dnssec-makekeyset.


creates two files with names based on the printed string. Knnnn.+aaa+iiiii.key contains the public key, and Knnnn.+aaa+iiiii.private contains the private key. The .key file contains a DNS KEY record that can be inserted into a zone file (directly or with a $INCLUDE statement). The .private file contains algorithm specific fields. For obvious security reasons, this file does not have general read permission. Both .key and .private files are generated for symmetric encryption algorithm such as HMAC-MD5, even though the public and private key are equivalent.


To generate a 768-bit DSA key for the domain example.com, the following command would be issued:

dnssec-keygen -a DSA -b 768 -n ZONE example.com

The command would print a string of the form:


In this example, dnssec-keygen creates the files Kexample.com.+003+26160.key and Kexample.com.+003+26160.private.

Related Information

The dnssec-makekeyset, dnssec-signkey, and dnssec-signzone, commands

The BIND 9 Administrator Reference Manual.

RFC 2535, RFC 2845, and RFC 2539.

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