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man pages section 1M: System Administration Commands

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Updated: July 2017



dnssec-keygen - DNSSEC key generation tool


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


The dnssec-keygen utility generates keys for DNSSEC (Secure DNS), as defined in RFC 2535 and RFC 4034. It can also generate keys for use with TSIG (Transaction Signatures), as defined in RFC 2845.


The following options are supported:

–a algorithm

Select the cryptographic algorithm. The value of algorithm must be one of RSAMD5 (RSA) or RSASHA1, DSA, NSEC3RSASHA1, NSEC3DSA, DH (Diffie-Hellman), or HMAC-MD5. These values are case insensitive.

For DNSSEC, RSASHA1 is a mandatory-to-implement algorithm and DSA is recommended. For TSIG, HMAC-MD5 is mandatory.

Note - HMAC-MD5 and DH automatically set the –k flag.
–b keysize

Specify the number of bits in the key. The choice of key size depends on the algorithm used. RSAMD5 and RSASHA1 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.

–c class

Indicate that the DNS record containing the key should have the specified class. If not specified, class IN is used.


Use a large exponent if generating an RSAMD5 or RSASHA1 key.

–f flag

Set the specified flag in the flag field of the KEY/DNSKEY record. The only recognized flag is KSK (Key Signing Key) DNSKEY.

–g generator

Use this generator if generating a Diffie Hellman key. 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.


Print a short summary of the options and arguments to dnssec-keygen.


Generate KEY records rather than DNSKEY records.

–n nametype

Specify the owner type of the key. The value of nametype must either be ZONE (for a DNSSEC zone key (KEY/DNSKEY)), HOST or ENTITY (for a key associated with a host (KEY)), USER (for a key associated with a user(KEY)), or OTHER (DNSKEY). These values are case insensitive. Defaults to ZONE for DNSKEY generation.

–p protocol

Set the protocol value for the generated key. The protocol argument is a number between 0 and 255. The default is 3 (DNSSEC) Other possible values for this argument are listed in RFC 2535 and its successors.

–r randomdev

Specify 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

Specify the strength value of the key. The strength argument is a number between 0 and 15, and currently has no defined purpose in DNSSEC.

–t type

Indicate 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

Set the debugging level.


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.

  • nnnn is the key name.

  • aaa is the numeric representation of the algorithm.

  • iiiii is the key identifier (or footprint).

The dnssec-keygen utility creates two files, with names based on the printed string.

  • Knnnn.+aaa+iiiii.key contains the public key.

  • 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.


Example 1 Generating a 768-bit DSA Key

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:


The following files would be created:



See attributes(5) for descriptions of the following attributes:

Interface Stability

See Also

dnssec-signzone(1M), attributes(5)

RFC 2539, RFC 2845, RFC 4033

See the BIND 9 Administrator's Reference Manual. As of the date of publication of this man page, this document is available at https://kb.isc.org/article/AA-01031https://kb.isc.org/article/AA-01031 .