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SoftHSM is part of the OpenDNSSEC project.

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OpenDNSSEC handles and stores its cryptographic keys via the PKCS#11 interface. This interface specifies how to communicate with cryptographic devices such as HSM:s (Hardware Security Modules) and smart cards. The purpose of these devices is, among others, to generate cryptographic keys and sign information without revealing private-key material to the outside world. They are often designed to perform well on these specific tasks compared to ordinary processes in a normal computer.

A potential problem with the use of the PKCS#11 interface is that it might limit the wide spread use of OpenDNSSEC, since a potential user might not be willing to invest in a new hardware device. To counter this effect, OpenDNSSEC is providing a software implementation of a generic cryptographic device with a PKCS#11 interface, the SoftHSM. SoftHSM is designed to meet the requirements of OpenDNSSEC, but can also work together with other cryptographic products because of the PKCS#11 interface.


SoftHSM depends on the Botan 1.8.0 or greater (a cryptographic library) and SQLite 3.3.9 or greater (a database library). But it is recommended to use Botan 1.8.5 or greater since there is a known issues on some OS which freezes the application when it tries to pull entropy. If the packaged version for your distribution does not work try to compile the latest version from source. They can be found at: and


Bulding and

Configure the installation/compilation scripts:



--with-botan=PATH       Specify prefix of path of Botan
--with-sqlite3=PATH     Specify prefix of path of SQLite3
--enable-64bit          Compile a 64-bit version
--with-loglevel=INT     The log level. 0=No log 1=Error 2=Warning 
                        3=Info 4=Debug (default INT=3)
--prefix=DIR            The installation directory
                        (default DIR=/usr/local)

For more options:

./configure --help

Compile the source code:


Install the library:

sudo make install


Add the tokens to the slots

The default location of the config file is /etc/softhsm.conf. This location can be change by setting the environment variable.

export SOFTHSM_CONF=/home/user/config.file

Open the config file and add the slots and tokens.

pico /home/user/config.file

# Comments can be added

Note: The token databases does not exist at this stage. The given paths are just an indication to SoftHSM on where it should store the information for each token. Each token are now treated as uninitialized.

Initialize your tokens

Use either the softhsm tool or the PKCS#11 interface. The SO PIN can e.g. be used to re-initialize the token and the user PIN is handed out to the application so it can interact with the token.

softhsm --init-token --slot 0 --label "My token 1"

Type in SO PIN and user PIN.

softhsm --init-token --slot 4 --label "A token"

Type in SO PIN and user PIN.

Using the library

Link to and use the PKCS#11 interface.

Key Management

It is possible to export and import keys to libsofthsm.

Importing a key pair

Use the PKCS#11 interface or the softhsm tool where you specify the path to the key file, slot number, label and ID of the new objects, and the user PIN. The file must be in PKCS#8 format.

softhsm --import key1.pem --slot 1 --label "My key" --id A1B2 --pin 123456

Add, --file-pin PIN, if the key file is encrypted. Use, softhsm --help, for more info.

Exporting a key pair

All keys can be exported from the token database by using the softhsm tool. The file will be exported in PKCS#8 format.

softhsm --export key2.pem --slot 1 --id A1B2 --pin 123456

Add, --file-pin PIN, if you want to output an encrypted file. Use, softhsm --help, for more info.

Converting Keys to/from BIND

The softhsm-keyconv tool can convert keys between BIND .private-key format and PKCS#8 key file format.

Convert from BIND .private to PKCS#8

Keys used for DNSSEC in BIND can be converted over to PKCS#8. Thus possible to import them into SoftHSM.

softhsm-keyconv --topkcs8 --in --out rsa.pem

Add, --pin PIN, if you want an encrypted PKCS#8 file. Use, softhsm-keyconv --help, for more info.

Convert from PKCS#8 to BIND .private and .key

PKCS#8 files can be converted to key used for DNSSEC signing in BIND. The public key is also saved to file.

softhsm-keyconv --tobind --in rsa.pem --name --ttl 3600 \
                --ksk --algorithm RSASHA1-NSEC3-SHA1

Add, --pin PIN, if you the PKCS#8 file is encrypted. Use, softhsm-keyconv --help, for more info.

The following files will be created in this example:


A token can be backed up by issuing the command:

sqlite3 PATH-TO-YOUR-TOKEN ".backup copy.db"

Copy the "copy.db" to a secure location. To restore the token, just copy the file back to the system and add it to a slot in the file softhsm.conf.

If you are using SQLite3 version < 3.6.11, then you have to use the command below. But it will not copy the "PRAGMA user_version", which is used by SoftHSM for versioning. So you have to do that manually. In this case the version number is 100.

sqlite3 PATH-TO-YOUR-TOKEN .dump | sqlite3 copy.db
sqlite3 copy.db "PRAGMA user_version = 100;"

Some attributes in the PKSC#11 API are defined as CK_ULONG, unsigned long integer, where the length of the data depends on the architecture (32-bit, 64-bit). The attributes are stored directly in the database. The database can thus not be moved between two systems with different architectures.


SoftHSM version 1, extended with EnigmaBridge API - remote HSM binding via classic PKCS#11 interface








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