DigitalNet Government Solutions has delivered the Version 2.4 S/MIME Freeware Library (SFL) source code. The SFL source code files and documents are freely available at
The SFL implements the IETF S/MIME v3 RFC 3369 Cryptographic Message Syntax (CMS) and RFC 2634 Enhanced Security Services (ESS) specifications. It implements portions of the RFC 2633 Message Specification, RFC 2632 Certificate Handling, and RFC 3370 CMS Algorithms specifications. When used in conjunction with the Crypto++ freeware library, the SFL implements the RFC 2631 Diffie-Hellman (D-H) Key Agreement Method
specification. It has been successfully tested using the Microsoft (MS) Windows 2000/XP, Linux and Sun Solaris 2.8 operating systems. Further enhancements, ports and testing of the SFL are still in process. Further releases of the SFL will be provided as significant capabilities are added.
The SFL has been successfully used to sign, verify, encrypt and decrypt
CMS/ESS objects using: DSA, E-S D-H, 3DES algorithms provided by the
Crypto++ library; RSA suite of algorithms provided by the RSA BSAFE 6.0
Crypto-C and Crypto++ libraries; and Fortezza suite of algorithms
provided by the Fortezza Crypto Card. The v2.4 SFL uses the v2.4
Certificate Management Library (CML) and v1.6 Enhanced SNACC (eSNACC)
ASN.1 C++ Library to encode/decode objects. The v2.4 SFL release
includes: SFL High-level library; Free (a.k.a. Crypto++) Crypto Token
Interface Library (CTIL); BSAFE CTIL; Fortezza CTIL; SPEX/ CTIL;
PKCS #11 CTIL; Microsoft CAPI v2.0 CTIL; test utilities; test drivers;
and test data. All CTILs were tested as Dynamically Linked Libraries
(DLL) using MS Windows. The Fortezza, BSAFE and Crypto++ CTILs
were tested with the respective security libraries as shared objects
using Linux and Solaris 2.8.
The SFL has been successfully used to exchange signedData and
envelopedData messages with the MS Internet Explorer Outlook Express
v4.01, Netscape Communicator 4.X, Entrust and Baltimore S/MIME
products. Signed messages have been exchanged with the RSA S/MAIL and
WorldTalk S/MIME v2 products.
The SFL has also been used to perform S/MIME v3 interoperability
testing with Microsoft that exercised the majority of the features
specified by RFCs 3369, 3370, 2631 and 2634. This testing included the
RSA, DSA, E-S D-H, 3DES, SHA and Fortezza algorithms. We used the SFL
to successfully process the SFL-supported sample data included in the
S/MIME WG "Examples of S/MIME Messages" document. We also used the
SFL to generate S/MIME v3 sample messages that were included in the
The use of the v2.4 SFL is described in the v2.4 SFL Application
Programming Interface (API) and v2.4 SFL Software Design Description
documents. The use of the v2.4 CTIL API is described in the v2.4
CTIL API document.
v2.4 SFL includes the following enhancements (compared to v2.3
SFL and CTIL releases):
1) Added support for the creation and processing of the RFC
3161-compliant Time Stamp Token content type.
2) Enhanced API to accomodate reciept hash.
3) Enhanced ASN.1 encode/decode functions with "Certificate Management
Messages over CMS".
v2.4 CTILs include the following enhancements (compared to v2.3 release):
1) Added PKCS#11 interface for Crypto++.
2) Added key generation library for generating public/private
key pairs, wrapping the private keys, and generating PKCS#12 files.
3) Added support for RFC 2437 PKCS #1 Optimal Asymetric Encryption Padding
(RSAES-OAEP) key transport method of key management.
The SFL is developed to maximize portability to 32-bit operating
systems. In addition to testing on MS Windows, Linux and Solaris 2.8,
we may port the SFL to other operating systems.
All source code for the SFL is being provided at no cost and with no
financial limitations regarding its use and distribution.
Organizations can use the SFL without paying any royalties or
licensing fees. DigitalNet is developing the SFL under contract to
the U.S. Government. The U.S. Government is furnishing the SFL
source code at no cost to the vendor subject to the conditions of
the "SFL Public License".
On 14 January 2000, the U.S. Department of Commerce, Bureau of
Export Administration published a new regulation implementing an update
to the U.S. Government's encryption export policy
. In accordance with
the revisions to the Export Administration Regulations (EAR) of 14 Jan
2000, the downloading of the SFL source code is not password controlled.
The SFL is composed of a high-level library that performs generic CMS
and ESS processing independent of the crypto algorithms used to
protect a specific object. The SFL high-level library makes calls to
an algorithm-independent CTIL API. The underlying, external crypto
token libraries are not distributed as part of the SFL source code.
The application developer must independently obtain these libraries and
then link them with the SFL.
The SFL uses the CML and eSNACC ASN.1 Library to encode/decode
certificates, ACs, CRLs and components thereof. The CML is freely
available at: <http://www.DigitalNet.com/knowledge/cml_home.htm>
The SFL has been successfully tested in conjunction with the Access
Control Library (ACL) that is freely available to everyone from:
The National Institute of Standards and Technology (NIST) is providing
test S/MIME messages (created by DigitalNet) at
DigitalNet used the SFL to successfully process the NIST test data.
NIST is using the SFL and CML as part of the NIST S/MIME Test
Facility (NSMTF) that they are planning to host (see
). Vendors will be able to use
the NSMTF to help determine if their products comply with the
IETF S/MIME v3 specifications and the Federal S/MIME v3 Client Profile.
The SFL has been integrated into many applications to provide CMS/ESS
security services. For example, the SFL was integrated into a security
plug-in for a commercial e-mail application that enabled the
application to meet the Bridge Certification Authority Demonstration
Phase II requirements including implementing ESS features such as
The Internet Mail Consortium (IMC) has established an SFL web page
. The IMC has also established an SFL
mail list which is used to: distribute information regarding SFL
releases; discuss SFL-related issues; and provide a means for SFL
users to provide feedback, comments, bug reports, etc. Subscription
information for the imc-sfl mailing list is at the IMC web site
All comments regarding the SFL source code and documents are welcome.
This SFL release announcement was sent to several mail lists, but
please send all messages regarding the SFL to the imc-sfl mail list
ONLY. Please do not send messages regarding the SFL to any of the IETF
mail lists. We will respond to all messages sent to the imc-sfl mail
Matthew J. Bertapelle
DigitalNet Government Solutions, LLC