Network Working Group IAB
Request for Comments: 1984 IESG
Category: Informational August 1996
IAB and IESG Statement on Cryptographic Technology and the Internet
Status of This Memo
This memo provides information for the Internet community. This memo
does not specify an Internet standard of any kind. Distribution of
this memo is unlimited.
Copyright
(C) Internet Society 1996. Reproduction or translation of the
complete document, but not of extracts, including this notice, is
freely permitted.
July 24, 1996
The Internet Architecture Board (IAB) and the Internet Engineering
Steering Group (IESG), the bodies which oversee architecture and
standards for the Internet, are concerned by the need for increased
protection of international commercial transactions on the Internet,
and by the need to offer all Internet users an adequate degree of
privacy.
Security mechanisms being developed in the Internet Engineering Task
Force to meet these needs require and depend on the international use
of adequate cryptographic technology. Ready access to such
technology is therefore a key factor in the future growth of the
Internet as a motor for international commerce and communication.
The IAB and IESG are therefore disturbed to note that various
governments have actual or proposed policies on access to
cryptographic technology that either:
(a) impose restrictions by implementing export controls; and/or
(b) restrict commercial and private users to weak and inadequate
mechanisms such as short cryptographic keys; and/or
(c) mandate that private decryption keys should be in the hands of
the government or of some other third party; and/or
(d) prohibit the use of cryptology entirely, or permit it only to
specially authorized organizations.
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RFC 1984 Cryptographic Technology August 1996
We believe that such policies are against the interests of consumers
and the business community, are largely irrelevant to issues of
military security, and provide only a marginal or illusory benefit to
law enforcement agencies, as discussed below.
The IAB and IESG would like to encourage policies that allow ready
access to uniform strong cryptographic technology for all Internet
users in all countries.
The IAB and IESG claim:
The Internet is becoming the predominant vehicle for electronic
commerce and information exchange. It is essential that the support
structure for these activities can be trusted.
Encryption is not a secret technology monopolized by any one country,
such that export controls can hope to contain its deployment. Any
hobbyist can program a PC to do powerful encryption. Many algorithms
are well documented, some with source code available in textbooks.
Export controls on encryption place companies in that country at a
competitive disadvantage. Their competitors from countries without
export restrictions can sell systems whose only design constraint is
being secure, and easy to use.
Usage controls on encryption will also place companies in that
country at a competitive disadvantage because these companies cannot
securely and easily engage in electronic commerce.
Escrow mechanisms inevitably weaken the security of the overall
cryptographic system, by creating new points of vulnerability that
can and will be attacked.
Export controls and usage controls are slowing the deployment of
security at the same time as the Internet is exponentially increasing
in size and attackers are increasing in sophistication. This puts
users in a dangerous position as they are forced to rely on insecure
electronic communication.
TECHNICAL ANALYSIS
KEY SIZE
It is not acceptable to restrict the use or export of cryptosystems
based on their key size. Systems that are breakable by one country
will be breakable by others, possibly unfriendly ones. Large
corporations and even criminal enterprises have the resources to
break many cryptosystems. Furthermore, conversations often need to
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RFC 1984 Cryptographic Technology August 1996
be protected for years to come; as computers increase in speed, key
sizes that were once out of reach of cryptanalysis will become
insecure.
PUBLIC KEY INFRASTRUCTURE
Use of public key cryptography often requires the existence of a
"certification authority". That is, some third party must sign a
string containing the user's identity and public key. In turn, the
third party's key is often signed by a higher-level certification
authority.
Such a structure is legitimate and necessary. Indeed, many
governments will and should run their own CAs, if only to protect
citizens' transactions with their governments. But certification
authorities should not be confused with escrow centers. Escrow
centers are repositories for private keys, while certification
authorities deal with public keys. Indeed, sound cryptographic
practice dictates that users never reveal their private keys to
anyone, even the certification authority.
KEYS SHOULD NOT BE REVEALABLE
The security of a modern cryptosystem rests entirely on the secrecy
of the keys. Accordingly, it is a major principle of system design
that to the extent possible, secret keys should never leave their
user's secure environment. Key escrow implies that keys must be
disclosed in some fashion, a flat-out contradiction of this
principle. Any such disclosure weakens the total security of the
system.
DATA RECOVERY
Sometimes escrow systems are touted as being good for the customer
because they allow data recovery in the case of lost keys. However,
it should be up to the customer to decide whether they would prefer
the more secure system in which lost keys mean lost data, or one in
which keys are escrowed to be recovered when necessary. Similarly,
keys used only for conversations (as opposed to file storage) need
never be escrowed. And a system in which the secret key is stored by
a government and not by the data owner is certainly not practical for
data recovery.
SIGNATURE KEYS
Keys used for signatures and authentication must never be escrowed.
Any third party with access to such keys could impersonate the
legitimate owner, creating new opportunities for fraud and deceit.
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RFC 1984 Cryptographic Technology August 1996
Indeed, a user who wished to repudiate a transaction could claim that
his or her escrowed key was used, putting the onus on that party. If
a government escrowed the keys, a defendant could claim that the
evidence had been forged by the government, thereby making
prosecution much more difficult. For electronic commerce, non-
repudiation is one of the most important uses for cryptography; and
non-repudiation depends on the assumption that only the user has
access to the private key.
PROTECTION OF THE EXISTING INFRASTRUCTURE
In some cases, it is technically feasible to use cryptographic
operations that do not involve secrecy. While this may suffice in
some cases, much of the existing technical and commercial
infrastructure cannot be protected in this way. For example,
conventional passwords, credit card numbers, and the like must be
protected by strong encryption, even though some day more
sophisticated techniques may replace them. Encryption can be added
on quite easily; wholesale changes to diverse systems cannot.
CONFLICTING INTERNATIONAL POLICIES
Conflicting restrictions on encryption often force an international
company to use a weak encryption system, in order to satisfy legal
requirements in two or more different countries. Ironically, in such
cases either nation might consider the other an adversary against
whom commercial enterprises should use strong cryptography. Clearly,
key escrow is not a suitable compromise, since neither country would
want to disclose keys to the other.
MULTIPLE ENCRYPTION
Even if escrowed encryption schemes are used, there is nothing to
prevent someone from using another encryption scheme first.
Certainly, any serious malefactors would do this; the outer
encryption layer, which would use an escrowed scheme, would be used
to divert suspicion.
ESCROW OF PRIVATE KEYS WON'T NECESSARILY ALLOW DATA DECRYPTION
A major threat to users of cryptographic systems is the theft of
long-term keys (perhaps by a hacker), either before or after a
sensitive conversation. To counter this threat, schemes with
"perfect forward secrecy" are often employed. If PFS is used, the
attacker must be in control of the machine during the actual
conversation. But PFS is generally incompatible with schemes
involving escrow of private keys. (This is an oversimplification,
but a full analysis would be too lengthy for this document.)
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RFC 1984 Cryptographic Technology August 1996
CONCLUSIONS
As more and more companies connect to the Internet, and as more and
more commerce takes place there, security is becoming more and more
critical. Cryptography is the most powerful single tool that users
can use to secure the Internet. Knowingly making that tool weaker
threatens their ability to do so, and has no proven benefit.
Security Considerations
Security issues are discussed throughout this memo.
Authors' Addresses
Brian E. Carpenter
Chair of the IAB
CERN
European Laboratory for Particle Physics
1211 Geneva 23
Switzerland
Phone: +41 22 767-4967
EMail: brian@dxcoms.cern.ch
Fred Baker
Chair of the IETF
cisco Systems, Inc.
519 Lado Drive
Santa Barbara, CA 93111
Phone: +1-805-681-0115
EMail: fred@cisco.com
The Internet Society is described at http://www.isoc.org/
The Internet Architecture Board is described at
http://www.iab.org/iab
The Internet Engineering Task Force and the Internet Engineering
Steering Group are described at http://www.ietf.org
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RFC, FYI, BCP