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id stringlengths 40 40	title stringlengths 15 120	text stringlengths 41 3.14k	source stringclasses 2 values
ee66982ff6659f4f05cac891608c14292943029e	hara's pseudo-random code system, like every additive system	hara's pseudo-random code system, like every additive system other than the one-time pad, can be broken. eventually someone, somewhere will use overlapping parts of the additive charts. the first thing the cryptanalyst does is identify where in the message the starting point of the chart (the "indicator") is hidden – t...	wikipedia
493a8fab7dea285a0d839390b3c7ebcc40a07fd0	superencipherment is fairly strong. it can be, and	superencipherment is fairly strong. it can be, and was, broken, but it is very hard to do. with the exception of the one-time pad, which will keep its secrets until the end of time, any code or cipher can be broken. all that is required is sufficient material. all that can be expected of a code or cipher system is that...	wikipedia
3d9af695d58e044d35ec88c970495be1543d644d	this system is not new. diplomats and armies	this system is not new. diplomats and armies started superenciphering with additives sometime during or soon after the first world war and by the 1920s it was common. german diplomats in paris were using, shortly after the first world war, a codebook of 100,000 groups superenciphered twice from a book of 60,000 additiv...	wikipedia
c5e881eb0d76d8184c6ffda9c68eb6e6a4ab2cd9	hara devised a system that used random numbers	hara devised a system that used random numbers to superencipher japanese army codes. possibly because of the logistical difficulties inherent in the one-time pad system, hara's system used tables of pseudo-random numbers. the encipherer had to indicate where in the table he (or much less likely at the time, she) did th...	wikipedia
5d22d362edd13a85be6680b321d81ca0985d7049	using random numbers for cryptography was first done	using random numbers for cryptography was first done around 1917 for securing teleprinter communications. it proved unfeasible for the reasons mentioned above. by the mid-1920s however, the german government was using one-time pads for diplomatic correspondence. they had learned their lessons from world war i and were ...	wikipedia
03d0f71d14c2897cb2fc1efe6052be5f998429d6	the " one-time pad " system is the	the " one-time pad " system is the only cipher system that is totally secure. it uses random numbers to encode the plaintext. if the numbers are truly random and the encoder never reuses those numbers, the encoded message cannot be broken. fortunately for cryptologists, random numbers are very difficult to come up with...	wikipedia
8a1fce706d067f705a76b1dc109b46bfeff75306	a two-part code mixes the lists, making the	a two-part code mixes the lists, making the code stronger by avoiding the problem described above. the drawback is that you now need two books. one, for encoding, has the plaintext in order to make encoding easy and the other, for decoding, has the code groups in order. hence the name "two-part" code. the increase in s...	wikipedia
ae4f43d9d1f128fb2a352cad7a7e325a89347847	it also makes it easier for the enemy	it also makes it easier for the enemy to break the code because once they realize they are dealing with a one-part code, they can use known groups to draw conclusions about unknown groups. for example, if the enemy knows that aabbc is antwerp and aabbz is available, they will know that aabbm cannot be tokyo.	wikipedia
e340038733e17248fae09ac7f224a62a42fa8620	code books contain two lists – one of	code books contain two lists – one of code groups and one of plaintext letters, words, and phrases. someone encoding a message looks up the words in the plaintext list and substitutes the corresponding code group. obviously it is important for that person's sanity that the plaintext be in some sort of order so words ca...	wikipedia
bd1ca0763dd170bcea8f77b9f2e9738761895956	neither takagawa nor hiyama provide details about when	neither takagawa nor hiyama provide details about when this three-number code system was adopted for army communications. a three-number code has a maximum of 10³, or 1000 groups — which is still too small for a strategic code and a far cry from the 25,000 that yardley claims some japanese codes had in the 1920s. howev...	wikipedia
efdc09e91c1b17c0b2fb7ac064ac3fa4b3734060	hara hisashi became head of the code section	hara hisashi became head of the code section of the seventh division sometime after 1932 and was later transferred to the third section of the army general staff. sometime between then and 1940, hara devised a system that used a pseudo-random number additive to superencipher the three number code the army already had i...	wikipedia
26044e3c6e5b449311056d56ca9171b765a8abea	regular polyalphabetic substitution ciphers often rely on code	regular polyalphabetic substitution ciphers often rely on code words to determine alphabet changes. each letters of the code work references a different alphabet. with the ten charts of hyakutake's system, a code number would be easy to use for pseudo-random changes – "301934859762" means encode the first word or phras...	wikipedia
8a0b68cb84b16d33f54b5bca41b758824e4ca45e	so switching charts after every couple of words	so switching charts after every couple of words is not as secure as switching after every word. also important for security is how the cryptographer switches between the charts. if hyakutake's system required the code clerk to switch codes charts pseudo-randomly, that would provide more security than requiring a set se...	wikipedia
5827e2e672be8303a73a726086682f2ec0f9fdcf	likewise, if code groups were used to indicate	likewise, if code groups were used to indicate a switch to a new chart, this could also have weakened the code unnecessarily. in fact, yardley specifically mentions it as making the codes easier to cryptanalyze. generally speaking, substitution systems switch alphabets as often as possible because that provides the bes...	wikipedia
b1a4c185552be76783d71ea1af49a4355e354a24	including more terms means that fewer have to	including more terms means that fewer have to be spelled out in kana – which is the whole point of using a code. further, the reduction in duplication allows more flexibility in assigning homophones. instead of ten groups for each letter, word, or phrase, each could receive homophones based on its frequency of occurren...	wikipedia
00bfacf402bd2ea1ecf3b5167387047fcdb4832b	the use of ten charts may have been	the use of ten charts may have been an illusory complication – rather than improve the security of the code, it probably made the code weaker. if, instead of ten different code groups for 626 terms, hyakutake had used the ten charts (with slight modification to make each group unique) to provide code groups for closer ...	wikipedia
c0538a465c764d089ce47b732f49b195abe6335e	so although hyakutake's new code system was original,	so although hyakutake's new code system was original, the fundamental idea underlying the system was well known, as were its weaknesses. with only 626 code groups, it is more cipher than code. as mentioned above, the ten different code charts just make it a polyalphabetic cipher – one with only ten "alphabets." methods...	wikipedia
cc9d16e817f6643e6be6b546c6f2aeb1eb4cbda1	with a bit of luck, experienced cryptanalysts have	with a bit of luck, experienced cryptanalysts have been able to break polyalphabetic ciphers for centuries. from the late 19th century they did not even need luck – auguste kerckhoffs published a general solution for polyalphabetic ciphers in 1883 in his book la cryptographie militaire.	wikipedia
ce7319b9e60f5010ca1565e9db0dbf030f5d1c82	it is clear from yardley's description that hyakutake's	it is clear from yardley's description that hyakutake's new system was not very effective. the system used 10 charts, each with 26 rows and columns labeled from a to z. this gives 626 two-letter code groups. most words and phrases will not be in the code and must be spelled out in kana. in this respect it is similar to...	wikipedia
7eacb8142e8b78217c6525c4f3a93ac9b4b8219b	yardley also describes the japanese system of sectioning	yardley also describes the japanese system of sectioning their messages but does not make it clear if this applies to the two-letter, ten-chart code. takagawa's description of hyakutake's code does not mention any sectioning but otherwise closely matches yardley's account. it is possible then that sectioning was not a ...	wikipedia
64310219a6c010d071f83ada18049bb906365fef	hyakutake harukichi was among the first group of	hyakutake harukichi was among the first group of japanese officers to study in poland and on his return was made the chief of the code section of the third department of the army general staff. this was in 1926. naturally enough, one of his first concerns was strengthening army codes. he started by designing a new syst...	wikipedia
f15575b491b592992f902fe2bfc00116d44e7dda	although they do mention kowalefsky (if not by	although they do mention kowalefsky (if not by name) neither kahn nor yardley mentions anything about japanese cryptologists training in poland or even kowalefsky returning home. thus, probably the most widely read english books on cryptological history are possibly missing a large and important part of the development...	wikipedia
0f22353c243d236ed95d57d4b5a34b8083c5f591	kahn writes that kowalefsky had been in japan	kahn writes that kowalefsky had been in japan from about 1920, when he was supposedly helping improve japanese codes, and was still there in 1925 to teach at a new navy code school. that is, kahn has kowalefsky working for the navy, not the army. japanese sources make it clear that both army and navy officers attended ...	wikipedia
c32786c14ccc2693ee347a6562ef4ce8474e9496	takagawa and hiyama both assert that each year	takagawa and hiyama both assert that each year for about the next fourteen (until shōwa 14) years, two japanese army officers traveled to warsaw for a year of cryptological training. neither smith nor budiansky mentions kowalefsky or anything about japanese officers studying in poland. yardley mentions the "polish expe...	wikipedia
678618cca459c495b7c0cf0b1541bff88fd1e2e7	when the course finished, someone suggested that the	when the course finished, someone suggested that the novice cryptologists get some practical experience working with the polish cryptologists in poland. the japanese students would go to poland with their teacher. arrangements were made and a study-abroad program of sorts was started. five officers left for poland with...	wikipedia
204b18be90244b236e70d6f46a845e9d35aa490c	the arrangements were made and on 7 september	the arrangements were made and on 7 september 1924, captain jan kowalefsky arrived in yokohama. kowalefsky taught a three-month joint army-navy course to at least seven officers: four from the army and three from the navy.	wikipedia
ba0f84aa3ad57b64f97320d6cac66f8b9c0e474e	the japanese army could not have asked for	the japanese army could not have asked for more distinguished teachers. polish cryptanalysts would later break early versions of the german enigma machine in 1932 and their work jump-started the french and british efforts to break later, more complicated, enigma machines. in the 1920s and 1930s it is accurate to say th...	wikipedia
dec1a9d82597de33295e38f66d9249613dd686d4	these two failures convinced the leaders of the	these two failures convinced the leaders of the japanese army that they needed some outside help and for geopolitical reasons, they decided to turn to the polish military. poland had fought the soviet union in 1920 and the japanese believed the poles would be receptive to the idea of teaching someone on the soviet unio...	wikipedia
b808420dde14f909075ff225588e0fd15ad82642	the second event also involved a failure to	the second event also involved a failure to decipher intercepts. starting in 1923, the army began intercepting european and american diplomatic radio communications. interception was difficult but the task of deciphering intercepted messages proved too much for the army cryptanalysts.	wikipedia
74c47f528cca83efed2c0f998e627f714da409e2	the first was an incident during the siberian	the first was an incident during the siberian intervention. the japanese army came into possession of some soviet diplomatic correspondence, but their cryptanalysts were unable decipher the messages. someone suggested asking the polish military to try cryptanalyzing them. it took the poles less than a week to break the...	wikipedia
df9b7d8218689d04ff6f1d4b8aab499abc9d663a	the polish cipher expert, jan kowalefsky, might not	the polish cipher expert, jan kowalefsky, might not have helped improve japanese codes before the washington naval conference but he did have a strong influence on japanese cryptography between the conference and world war ii. he trained what seems to be the first generation of professional japanese cryptographers.	wikipedia
816f59db9add5c5ce21f6f1fbdb40a76bca5ba45	thus, the situation between the washington naval conference	thus, the situation between the washington naval conference and the mid-1920s was not that of a polish officer helping to make japanese codes much more secure. rather, japanese cryptographers were working to bring their codes up to the level of other major governments.	wikipedia
594fbe271da23be9196810602e03f1769c9ca448	however, it seems unlikely that the japanese government	however, it seems unlikely that the japanese government was using codebooks with 25,000 groups in the early 1920s. jumping from the weak code used for the washington naval conference to a book code of 25,000 in just a few years seems too fast, especially without some external indication that their codes had been compro...	wikipedia
4803996053a8abd604af87cddc197bcdfed91819	if, as yardley claims, some japanese codes did	if, as yardley claims, some japanese codes did have as many as 25,000 code groups at the time of the washington naval conference, it would indicate a healthy appreciation of cryptological realities. cryptographers have long known that bigger codes are better – all else being equal, a 25,000 group code is stronger than ...	wikipedia
00cf0b798ee8ce41be529ccb48af75a44aec2363	japanese cryptographers supposedly improved their codes through sectioning	japanese cryptographers supposedly improved their codes through sectioning – breaking the message into parts and rearranging them prior to encoding. this buries stereotypical openings and closings, which makes it harder for cryptanalysts to make initial breaks into a code by guessing at probable words. the technique is...	wikipedia
38274d5ac38b38887971e90689da07645c12fec1	it is possible that yardley is simply wrong	it is possible that yardley is simply wrong and japanese codes did not improve significantly between 1919 and 1924. kahn found that one improvement yardley mentions – three letter code groups mixed in with two letter groups – was not actually present in the japanese telegram that yardley claimed it was.	wikipedia
dc5c6a142f2404fca8c9a9208e0cf1b4e8c6bacb	a possibility that is ripe for further research,	a possibility that is ripe for further research, is that japanese cryptologists studied one or more of the books on codes and ciphers that were occasionally published in europe and america. for example, parker hitt's 1916 book manual for the solution of military ciphers was hugely popular, selling around 16,000 copies ...	wikipedia
f5f14dbf3a9cc50a87d95d30b380525f5352b982	yardley was right about a polish expert visiting	yardley was right about a polish expert visiting japan but he was mistaken about the timing. the japanese army did bring in a polish expert, jan kowalefsky, but he did not arrive in japan until september 1924. if japanese codes improved significantly between 1919 and 1924, as yardley claims, the improvements were the w...	wikipedia
78d197294d8881b8dd5b1e404717c7ba8865f727	thus the japanese diplomatic code in use in	thus the japanese diplomatic code in use in 1919 was extremely weak and fundamentally flawed: a diplomatic code that does not contain code groups for common geopolitical names and phrases but requires them to be spelled out cannot be considered strong. spelling out "stop" is further evidence that the code was not well ...	wikipedia
80c85a287356f8489294d5609cc4d9eb14ce0ab6	as can be seen from the description of	as can be seen from the description of yardley's original break into the code, groups were assigned to kana like "do" and "bo" which in japanese are not part of the regular alphabet but are created from other kana by adding pronunciation marks. providing for these non-alphabet kana would require at least another 25 and...	wikipedia