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Export of cryptography
Since World War II, Western governments, including the U.S. and its NATO allies have regulated the export of cryptography for national security considerations. In light of the enormous impact of cryptanalysis in WWII, it was abundantly clear to these governments that denying current and potential enemies access to cryptographic systems looked to be militarily valuable. They also wished to monitor the diplomatic communications of other nations, including the many new nations that were emerging in the post-colonial period and whose position on Cold War issues was regarded as vital. Since the U.S. and U.K. had, they believed, developed more advanced cryptographic capabilities than others, there arose a notion that controlling all dissemination of the more effective crypto techniques might be beneficial. Legal limitations made controlling all use of cryptography inside the U.S. difficult, but controlling access to U.S. developments by others was thought to be more practical -- there were at least no Constitutional impediments. Accordingly, regulations were introduced as part of munitions controls which required licenses to export cryptographic methods (and even their description); the regulations established that cryptography beyond a certain strength (defined by algorithm and length of key) would not be licensed for export except on a case-by-case basis. The expectation seems to have been that this would further national interests in reading 'their' communications and prevent others from reading 'ours'. This policy was also adopted elsewhere for various reasons.
The development, and public release, of DES and asymmetric key techniques in the 1970s, the rise of the Internet, and the willingness of some to risk and resist prosecution, eventually made this policy impossible to enforce, and by the late 1990s it was being relaxed in the US, and to some extent (eg, France), elsewhere. Nevertheless, some officials in the U.S. still believe that wide-spread availability of 'strong' cryptography world-wide has hampered the ability of the NSA to read intercepted communications that might reveal important information about intentions hostile to the U.S. and that, had the relaxation not happened, NSA would have had (and would have in future) an easier time. Others feel that the export controls in place in the last half of the 20th century discouraged incorporation of widely-known cryptographic tools into commercial products, particularly personal computer operating systems, and are a root cause of the present crisis in information security, aside from interfering with U.S. trade in such products. They observe that many of the advances, including asymmetric key cryptography and many of its algorithms, were already public in any case.
Pre-World War II
State control of secret communications, and usually the means which permit the secrecy, have been important since ancient Greece and perhaps before. Cryptographic methods have generally been among a nation's most closely guarded secrets. Since at least the 19th century, disclosure of those means, or of the plaintext of messages protected by them, has been generally treated as treason and handled accordingly. With the development of electrical communication, first the telegraph and then wireless, governments and commercial interests have needed to use codes and cyphers to protect their communications or to reduce cable costs. Since the demonstration of the benefits of wireless in WWI, the publication by Admiral Jackie Fisher and Winston Churchill in the 20's of the fact of that the English read German Naval codes in WWI, the revelation on two occasions (also in the 20s) by UK ministers of information that could only have come from reading encrypted Soviet messages, and the publication of Herbert Yardley's book, The American Black Chamber, in 1931 (revealing major breaks of diplomatic cryptography -- especially in connection with the Washington Naval Conference), nations had even more motivation than before to attempt to protect the communications confidentiality. With the development of high quality cryptographic techniques during and after WWI, particularly commercial availability of rotor machines, some of these techniques became publicly available, even commercially. The US had a de facto policy (later made de jure) of not permitting the patenting of 'important' cryptographic and other security related inventions, which, at least for US inventions, limited public release of some techniques. There are several publicly known examples, including several innovations associated with cypher equipment like SIGABA. Inventors so treated are known to have included William F. Friedman and Frank Rowlett. Other countries have had similar policies.
World War II
Virtually all trade between the Allies and the Axis was halted during WW II; that discovered was typically treated criminally, no matter what items were involved. Two of the Allies, the U.S. and the U.K., developed an especially close relationship that included exchanges of information on their deepest secrets, cryptography/cryptanalysis, RADAR and nuclear weapons research. While they provided large amounts of military equipment to its other major ally, the USSR, there is no record that any cryptographic assistance was provided; with the still speculative possibility that the Lucy spy ring as a covert information transfer channel. Indeed, the U.S. and U.K. were attempting to break Soviet codes until mid 1941 and, though the UK stopped even intercepting them then, the US continued to intercept and examine Soviet traffic. While Soviet cryptography was often quite sophisticated, a small part of the interecepted traffic was decrypted over the next 20 years.
Cold War era
In the early days of the cold war, the U.S. and its allies developed an elaborate series of export control regulations designed to prevent a wide range of supposedly superior Western technology from falling into the hands of others, particularly the Soviet bloc. All export of technology classed as 'critical' required a license. CoCom was organized to coordinate Western export controls.
Two types of technology were protected: technology associated only with weapons of war and dual use technology, which also had commercial applications. In the U.S., dual use technology export was controlled by the Department of Commerce, while munitions were controlled by the State Department. Encryption technology (techniques as well as equipment and, after computers became important, crypto software) was classified as a munition. However, this hardly mattered in practice since secure encryption was not, certainly in the immediate post War period, available to the general public.
The U.S. Government's introduction of the Data Encryption Standard in 1975 meant that commercial uses of high quality encryption would become common, and serious problems of export control began to arise. Generally these were dealt with through case-by-case export license request proceedings brought by computer manufacturers, such as IBM, and by their large corporate customers.
Encryption export controls became a matter of public concern with the introduction of the personal computer. Phil Zimmermann's PGP cryptosystem and its distribution on the Internet in 1991 was the first major 'individual level' challenge to controls on export of cryptography. The growth of electronic commerce in the 1990s created additional pressure for reduced restrictions. Shortly afterward, Netscape's SSL technology was widely adopted as a method for protecting credit card transactions using public key cryptography.
SSL encrypted messages using the RC4 cipher, and used 128-bit keys. U.S. government export regulations would not permit crypto systems using 128-bit keys to be exported. The longest key size allowed for export without individual license proceedings was 40 bits, so Netscape developed two versions of its web browser. The "U.S." edition had the full 128-bit strength. The "International Edition" had its effective key length reduced to 40-bits by revealing 88 bits of the key in the SSL protocol. Acquiring the 'U.S. domestic' version turned out to be sufficient hassle that most computer users, even in the U.S., ended up with the 'International' version, whose weak 40-bit encryption could be broken in a matter of days using a single personal computer. Much the same thing happened with Lotus Notes and for the same reasons.
Legal challenges by civil libertarians and privacy advocates, the wide spread availability of encryption software outside the U.S., and the perception by many corporate interests that adverse publicity about weak encryption was limiting their sales and the growth of e-commerce, led to a series of relaxations in US export controls, culminating in 1996 in the effective elimination of export controls on mass-market "shrinkwrap" and open source software containing cryptography (which, in any case, a "rogue state" could have downloaded, and subsequently verified, from file sharing networks or servers outside the US).
Cryptography exports from the U.S. are now (as of 2004) controlled by the Department of Commerce's Bureau of Industry and Security. Some restrictions still exist, even on mass market products, particularly with regard to export to "rogue states" and terrorist organizations. Militarized encryption equipment, TEMPEST-approved electronics, custom cryptographic software, and even cryptographic consulting services still require an export license. The regulations, though relaxed from pre-1996 standards, are still complex, and often require expert legal and cryptographic consulation. Other countries, notably those participating in the Wassenaar Arrangement, have similar restrictions.
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