dnssec-keygen — DNSSEC key generation tool


dnssec-keygen [-a algorithm] [-b keysize] [-n nametype] [-3] [-A date/offset] [-C] [-c class] [-D date/offset] [-e] [-f flag] [-g generator] [-h] [-K directory] [-k] [-P date/offset] [-p protocol] [-R date/offset] [-r randomdev] [-s strength] [-t type] [-U date/offset] [-v level] [-z] {name}


dnssec-keygen 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, or TKEY (Transaction Key) as defined in RFC 2930.


-a algorithm

Selects the cryptographic algorithm. For DNSSEC keys, the value of algorithm must be one of RSAMD5, RSASHA1, DSA, NSEC3RSASHA1, or NSEC3DSA. For TSIG/TKEY, the value must be DH (Diffie Hellman), HMAC-MD5, HMAC-SHA1, HMAC-SHA224, HMAC-SHA256, HMAC-SHA384, or HMAC-SHA512. These values are case insensitive.

If no algorithm is specified, then RSASHA1 will be used by default, unless the -3 option is specified, in which case NSEC3RSASHA1 will be used instead.

Note 1: that for DNSSEC, RSASHA1 is a mandatory to implement algorithm, and DSA is recommended. For TSIG, HMAC-MD5 is mandatory.

Note 2: DH, HMAC-MD5, and HMAC-SHA1 through HMAC-SHA512 automatically set the -T KEY option.

-b keysize

Specifies the number of bits in the key. The choice of key size depends on the algorithm used. RSAMD5 / 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.

The key size does not need to be specified if using a default algorithm. The default key size is 1024 bits for zone signing keys (ZSK's) and 2048 bits for key signing keys (KSK's, generated with -f KSK). However, if an algorithm is explicitly specified with the -a, then there is no default key size, and the -b must be used.

-n nametype

Specifies 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.


Use an NSEC3-capable algorithm to generate a DNSSEC key. If this option is used and no algorithm is explicitly set on the command line, NSEC3RSASHA1 will be used by default.


Compatibility mode: generates an old-style key, without any metadata. By default, dnssec-keygen will include the key's creation date in the metadata stored with the private key, and other dates may be set there as well (publication date, activation date, etc). Keys that include this data may be incompatible with older versions of BIND; the -C option suppresses them.

-c class

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


If generating an RSAMD5/RSASHA1 key, use a large exponent.

-f flag

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

-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.


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

-K directory

Sets the directory in which the key files are to be written.


Deprecated in favor of -T KEY.

-p protocol

Sets the protocol value for the generated key. The protocol 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

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 rrtype

Specifies the resource record type to use for the key. rrtype must be either DNSKEY or KEY. The default is DNSKEY when using a DNSSEC algorithm, but it can be overridden to KEY for use with SIG(0).

Using any TSIG algorithm (HMAC-* or DH) forces this option to KEY.

-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.


Dates can be expressed in the format YYYYMMDD or YYYYMMDDHHMMSS. If the argument begins with a '+' or '-', it is interpreted as an offset from the present time. If such an offset is followed by one of the characters 'y', 'm', 'w', 'd', or 'h', then the offset is computed in years, months, weeks, days, or hours, respectively; otherwise it is computed in seconds.

-P date/offset

Sets the date on which a key is to be published to the zone. After that date, the key will be included in the zone but will not be used to sign it.

-A date/offset

Sets the date on which the key is to be activated. After that date, the key will be included and the zone and used to sign it.

-R date/offset

Sets the date on which the key is to be revoked. After that date, the key will be flagged as revoked. It will be included in the zone and will be used to sign it.

-U date/offset

Sets the date on which the key is to be unpublished. After that date, the key will no longer be included in the zone, but it may remain in the key repository.

-D date/offset

Sets the date on which the key is to be deleted. After that date, the key can be removed from the key repository. NOTE: Keys are not currently deleted automatically; this field is included for informational purposes and for future development.


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).

dnssec-keygen 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 algorithms such as HMAC-MD5, even though the public and private key are equivalent.


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

dnssec-keygen -a DSA -b 768 -n ZONE

The command would print a string of the form:

In this example, dnssec-keygen creates the files and


dnssec-signzone(8), BIND 9 Administrator Reference Manual, RFC 2539, RFC 2845, RFC 4033.


Internet Systems Consortium