dnssec-keygen(1)

NAME

dnssec-keygen — key generation tool for DNSSEC

SYNOPSIS

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

DESCRIPTION

dnssec-keygen generates keys for Secure DNS (DNSSEC) as defined in RFC2535. It also generates keys for use in Transaction Signatures (TSIG) which is defined in RFC2845.

Argument

name: Specifies the domain name for which the key is to be generated.

Options

-a algorithm

This option is used to specify the encryption algorithm. The algorithm can be RSAMD5, DH, DSA or HMAC-MD5. RSA can also be used, which is equivalent to RSAMD5.

The algorithm argument identifying the encryption algorithm is case-insensitive. DNSSEC specifies DSA as a mandatory algorithm and RSA as a recommended one. Implementations of TSIG must support HMAC-MD5.

-b keysize

This option is used to determine the number of bits in the key. The choice of key size depends on the algorithm that is used.

If RSA algorithm is used, keysize must be between 512 and 2048 bits.

If the DH (Diffie-Hellman) algorithm is used, keysize must be between 128 and 4096 bits.

If the DSA (Digital Signature Algorithm) is used, keysize must be between 512 and 1024 bits and a multiple of 64.

If the HMAC-MD5 algorithm is used, keysize should be between 1 and 512 bits.

-e

This option is used for generating RSA keys with a large exponent value.

-g generator

This option is used when creating Diffie-Hellman keys. The -g option selects the Diffie-Hellman generator that is to be used. The only supported values for generator are 2 and 5. If no Diffie-Hellman generator is supplied, a known prime from RFC2539 will be used if possible; otherwise, 2 will be used as the generator.

-h

A summary of the options and arguments to dnssec-keygen is printed by this option.

-n nametype

This option specifies how the generated key will be used.

nametype can be either ZONE, HOST, ENTITY, or USER to indicate that the key will be used for signing a zone, host, entity or user; respectively. In this context HOST and ENTITY are identical. nametype is case-insensitive.

-p protocol-value

This option sets the protocol value for the generated key to protocol-value. The default is 2 (email) for keys of the type USER and 3 (DNSSEC) for all other key types. Other possible values for this argument are listed in RFC2535 and its successors.

-r randomdev

This option overrides the behaviour of dnssec-keygen to use random numbers to seed the process of generating keys when the system does not have a /dev/random device to generate random numbers. The dnssec-keygen program will prompt for keyboard input and use the time intervals between keystrokes to provide randomness. With this option it will use randomdev as a source of random data.

-s strength-value

This option is used to set the key's strength value. The generated key will sign DNS resource records with a strength value of strength-value. It should be a number in the range 0-15. The default strength is zero. The key strength field currently has no defined purpose in DNSSEC.

-t type

This option indicates if the key is used for authentication or confidentiality. type can be either AUTHCONF, NOAUTHCONF, NOAUTH or NOCONF. The default is AUTHCONF. If type is AUTHCONF, the key can be used for authentication and confidentiality. Setting type to NOAUTHCONF indicates that the key cannot be used for authentication or confidentiality. A value of NOAUTH means the key can be used for confidentiality but not for authentication. Similarly, NOCONF defines that the key cannot be used for confidentiality though it can be used for authentication.

-v level

This option can be used to make dnssec-keygen more verbose. As the debugging/tracing level increases, dnssec-keygen generates increasingly detailed reports about what it is doing. The default level is zero.

Generated Keys

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

The nnnn part is the dot-terminated domain name given by name. The DNSSEC algorithm identifier is indicated by aaa: 001 for RSA, 002 for Diffie-Hellman, 003 for DSA, or 157 for HMAC-MD5. iiiii is a five-digit number identifying the key.

dnssec-keygen creates two files. The file names are adapted from the key identification string above. They have names in the form:

Knnnn.+aaa+iiiii.key and
Knnnn.+aaa+iiiii.private.

These contain the public and private parts of the key respectively. The files generated by dnssec-keygen follow this naming convention to make it easy for the signing tool dnssec-signzone to identify which file(s) have to be read to find the necessary key(s) for generating or validating signatures.

The .key file contains a KEY resource record that can be inserted into a zone file with a $INCLUDE statement. The private part of the key is in the .private file. It contains details of the encryption algorithm that was used and any relevant parameters: prime number, exponent, modulus, subprime, etc. For obvious security reasons, this file does not have general read permission. The private part of the key is used by dnssec-signzone to generate signatures and the public part is used to verify the signatures. Both .key and .private key files are generated by symmetric encryption algorithm such as HMAC-MD5, even though the public and private key are equivalent.

EXAMPLE

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 

dnssec-keygen has printed the key identification string Kexample.com.+003+26160, indicating a DSA key with identifier 26160. It would have created the files

Kexample.com.+003+26160.key and
Kexample.com.+003+26160.private

containing the public and private keys respectively for the generated DSA key.

FILES

/dev/random

BUGS

The naming convention for the public and private key files is a little clumsy. It won't work for domain names that are longer than 236 characters because the .+aaa+iiiii.private suffix results in filenames that are too long for most UNIX systems.