In his other life, he allegedly was spying for the Russian government. Hanssen's deception was finally discovered, and in February he was arrested and later pled guilty to 15 espionage-related charges.
Spies are probably the world's best liars, because they have to be, but most of us practice deception on some level in our daily lives, even if it's just telling a friend that his horrible haircut "doesn't look that bad. Most often, lying is a defense mechanism used to avoid trouble with the law, bosses or authority figures. Sometimes, you can tell when someone's lying, but other times it may not be so easy.
Polygraphs , commonly called "lie detectors," are instruments that monitor a person's physiological reactions. These instruments do not, as their nickname suggests, detect lies. They can only detect whether deceptive behavior is being displayed. Do you think you can fool a polygraph machine and examiner? In this article, you'll learn how these instruments monitor your vital signs, how a polygraph exam works and about the legalities of polygraph testing.
A polygraph instrument is basically a combination of medical devices that are used to monitor changes occurring in the body. As a person is questioned about a certain event or incident, the examiner looks to see how the person's heart rate , blood pressure , respiratory rate and electro-dermal activity sweatiness, in this case of the fingers change in comparison to normal levels. Fluctuations may indicate that person is being deceptive, but exam results are open to interpretation by the examiner.
Polygraph exams are most often associated with criminal investigations, but there are other instances in which they are used. You may one day be subject to a polygraph exam before being hired for a job: Many government entities, and some private-sector employers, will require or ask you to undergo a polygraph exam prior to employment.
Polygraph examinations are designed to look for significant involuntary responses going on in a person's body when that person is subjected to stress, such as the stress associated with deception. The exams are not able to specifically detect if a person is lying, according to polygrapher Dr.
Bob Lee , former executive director of operations at Axciton Systems , a manufacturer of polygraph instruments. But there are certain physiological responses that most of us undergo when attempting to deceive another person.
The polygraph instrument has undergone a dramatic change in the last decade. For many years, polygraphs were those instruments that you see in the movies with little needles scribbling lines on a single strip of scrolling paper. These are called analog polygraphs. Today, most polygraph tests are administered with digital equipment. The scrolling paper has been replaced with sophisticated algorithms and computer monitors. Deceptive behavior is supposed to trigger certain physiological changes that can be detected by a polygraph and a trained examiner, who is sometimes called a forensic psychophysiologist FP.
This examiner is looking for the amount of fluctuation in certain physiological activities. Here's a list of physiological activities that are monitored by the polygraph and how they are monitored:.
As the examiner asks questions, signals from the sensors connected to your body are recorded on a single strip of moving paper. You will learn more about the examiner and the test itself later. Detractors of the polygraph call lie detection a voodoo science, saying that polygraphs are no more accurate at detecting lies than the flip of a coin. There's no such thing as lie detection.
I couldn't tell you what a lie looks like. He does assert that polygraphs can detect deceptive behavior even through the stress brought on by the exam itself. Through the specific procedure that the FP will employ, anxiety will not penetrate into it. In the next section, you will learn more about who polygraph examiners are and what makes them qualified to conduct these examinations.
Today, some polygraph examiners prefer to be called forensic psychophysiologists FPs. I'm looking for the innocent person. I'm their advocate. I'm totally unbiased and neutral when that person comes walking in.
But as soon as I make that assessment that there's no deception indicated, I immediately become their advocate. How the question is presented can greatly affect the results of a polygraph exam. There are several variables that an FP has to take into consideration, such as cultural and religious beliefs. Some topics may, by their mere mention, cause a specific reaction in the test subject that could be misconstrued as deceptive behavior.
The design of the question affects the way the person processes the information and how he or she responds. We made extensive efforts to be briefed on the technical details of the JHU-APL methodology, but although we were supplied with the executable program for the algorithms, the documentation provided to us offered insufficient details to allow for replication and verification of the claims made about their construction and performance. JHU-APL was unresponsive to repeated requests for detail on these matters, as well as on its process for building and validating its models.
On multiple occasions we were told either that the material was proprietary or that reports and testing were not complete and thus could not be shared. From the information available, we find that efforts to use technological advances in computerized recording to develop computer-based algorithms that can improve the interpretations of trained numerical evaluators have failed to build a strong theoretical rationale for their choice of measures. They have also failed to date to provide solid evidence of the performance of their algorithms on independent data with properly determined truth for a relevant population of interest.
As a result, we believe that their claimed performance is highly likely to degrade markedly when applied to a new research population and is even vulnerable to the prospect of substantial disconfirmation. In conclusion, computerized scor-.
We end with a cautionary note. A polygraph examination is a process involving the examiner in a complex interaction with the instrument and the examinee. Computerized scoring algorithms to date have not addressed this aspect of polygraph testing. For example, they have treated variations in comparison questions across tests as unimportant and have not coded for the content of these questions or analyzed their possible effect on the physiological responses being measured. Also, examiners may well be picking up a variety of cues during the testing situation other than those contained in the tracings even without awareness and letting those cues affect the judgments about the tracings.
Little evidence is available from the research literature on polygraph testing concerning this possibility, but until definitive evidence is available, it might be wise to include both computerized scoring and independent hand scoring as inputs to a decision process.
In most screening applications, information from polygraph examinations chart and interview information is not by itself determinative of personnel actions. Thus, polygraph information is often combined in some way with other information. We have been unable to determine whether DOE or any other federal agency has a standard protocol for combining such information or even any encoded standard practice, analogous to the ways the results of different diagnostic tests are combined in medicine to arrive at a diagnosis.
We made repeated requests for the DOE adjudication manual, which is supposed to encode the procedures for considering polygraph results and other information in making personnel decisions. We were initially told that the manual existed as a privileged document for official use only; after further requests, we were told that the manual is still in preparation. Thus it appears that various information sources are combined an in informal way on the basis of the judgment of adjudicators and other personnel.
Quality control for this phase of decision making appears to take the form of review by supervisors and of policies allowing employees to contest unfavorable personnel decisions. There are no written standards for how polygraph information should be used in personnel decisions at DOE, or, as far as we were able to determine, at any other agency.
We believe that any agency that uses polygraphs as part of a screening process should, in light of the inherent fallibility of the polygraph instrument, use the polygraph results only in conjunction with other information, and only as a trigger for further testing and investigation.
Policy decisions about using the polygraph must consider not only its accuracy and the tradeoffs it presents involving true positives and false positives and negatives, but also whether including the polygraph with the sources of information otherwise available improves the accuracy of detection and makes the tradeoffs more attractive.
This is the issue of incremental validity discussed in Chapter 2. It makes sense to use the polygraph in security screening if it adds information relevant to detecting security risks that is not otherwise available and with acceptable tradeoffs.
Federal agencies use or could use a variety of information sources in conjunction with polygraph tests for making personnel security decisions: background investigations, ongoing security checks by various investigative techniques, interviews, psychological tests, and so forth see Chapter 6.
We have not located any scientific studies that attempt directly to measure the incremental validity of the polygraph when added to any of these information sources. That is, the existing scientific research does not compare the accuracy of prediction of criminal behavior or any other behavioral criterion of interest from other indicators with accuracy when the polygraph is added to those indicators. Security officials in several federal agencies have told us that the polygraph is far more useful to them than background checks or other investigative techniques in revealing activities that lead to the disqualification of applicants from employment or employees from access to classified information.
It is impossible to determine whether the incremental. There are several scientifically defensible approaches to combining different sources of information that could be used as part of polygraph policies. The problem has been given attention in the extensive literature on decision making for medical diagnosis, classification, and treatment, a field that faces the problem of combining information from clinical observations, interviews, and a variety of medical tests see the more detailed discussion in Appendix K.
Statistical methods for combining data of different types e. In one, called independent parallel testing, a set of tests is used and a target result on any one is used to make a determination. For example, a positive result on any test may be taken to indicate the presence of a condition of interest.
In the other approach, called independent serial testing, if a particular test in the sequence is negative, the individual is concluded to be free of the condition of interest, but if the test is positive, another test is ordered. Validating a combined test of either type requires independent tests or sources of information and a test evaluation sample that is representative of the target population.
Serial screening and its logic are familiar from many medical settings. A low-cost test of moderate accuracy is usually used as an initial screen, with the threshold usually set to include a high proportion of the true positive cases people with the condition among those who test positive.
Most of those who test positive will be false positives, especially if the condition has a low base rate. In this approach, people who test positive are then subject to a more accurate but more expensive or invasive second-stage test, and so on through as many stages as warranted.
For example, mammograms and prostate-specific antigen PSA tests are among the many first screens used for detecting cancers, with biopsies as possible second-stage tests. The low cost of polygraph testing relative to detailed security investigation makes the polygraph attractive for use early in the screening series.
Detailed investigation could act as the second-stage test. Such a policy presents a bit of a dilemma. If the purpose of using the polygraph is like that of cancer screening—to avoid false negatives—the threshold should be set so as to catch a high proportion of spies or terrorists.
The result of this approach, in a population with a low base rate of spies or terrorists, is to greatly increase the number of false positives and the accompanying expense of investigating all the positives with traditional methods. The costs of detailed investigations can be reduced by setting the threshold so that few examinees are judged to show significant response.
However, setting such a friendly threshold runs the risk of an unacceptably high number of false negative results. A way might be found to minimize this dilemma if there were other independent tests that could be added in the sequence, either before the polygraph or between the polygraph and detailed investigation. Such tests would decrease the number of people who would have to pass the subsequent screens.
If such a screen could be applied before the polygraph, its effect would be to increase the base rate of target people spies, terrorists, or whatever among those given the polygraph by culling out large numbers of the others.
The result would be that the problem of high false positive rates in a population with a low base rate would be significantly diminished see Figures and , above. If such an independent screen could be applied after the polygraph, the result would be to reduce the numbers and costs of detailed investigations by eliminating more of the people who would eventually be cleared.
However, there is no test available that is known to be more accurate than the polygraph and that could fill the typical role of a second-stage test in serial screening. We have not found any scientific treatments of the relative benefits of using the polygraph either earlier or later in a series of screening tests, nor even any explicit discussion of this issue. We have also not found any consideration or investigation of the idea of using other tests in sequence with the polygraph in the manner described above.
The costs and benefits of using the polygraph at different positions in a sequence of screening tests needs careful attention in devising any policy that uses the polygraph systematically as a source of information in a serial testing model for security screening.
Some people have suggested that polygraph data could be analyzed and combined with other data by nonstatistical methods that rely on expert systems. There is disagreement on how successful such systems. For screening uses of the polygraph, it seems clear that no such body of knowledge exists. Lacking such knowledge, the serious problems that exist in deriving and adequately validating procedures for computer scoring of polygraph tests discussed above also exist for the derivation and validation of expert systems for combining polygraph results with other diagnostic information.
Insufficient scientific information exists to support recommendations on whether or how to combine polygraph and other information in a sequential screening model. A number of psychophysiological techniques appear promising in the long run but have not yet demonstrated their validity.
Some indicators based on demeanor and direct investigation appear to have a degree of accuracy, but whether they add information to what the polygraph can provide is unknown see Chapter 6.
The practical use of polygraph testing is shaped in part by its legal status. Polygraph testing has long been the subject of judicial attention, much more so than most forensic technologies. In contrast, courts have only recently begun to look at the data, or lack thereof, for other forensic technologies, such as fingerprinting, handwriting identification and bite marks, which have long been admitted in court.
The attention paid to polygraphs has generally led to a skeptical view of them by the judiciary, a view not generally shared by most executive branch agencies.
Judicial skepticism results both from questions about the validity of the technology and doubt about its need in a constitutional process that makes juries or judges the finders of fact. Doubts about polygraph tests also arise from the fact that the test itself contains a substantial interrogation component. Courts recognize the usefulness of interrogation strategies, but hesitate when the results of an interrogation are presented as evidentiary proof.
Although polygraphs clearly have utility in some settings, courts have been unwilling to conclude that utility denotes validity. The value of the test for law enforcement and employee screening is an amalgam of utility and validity, and the two are not easily separated. An early form of the polygraph served as the subject of the wellknown standard used for evaluating scientific evidence—general acceptance—announced in Frye v. United States and still used in some courts see below.
It has been the subject of a U. Supreme Court decision, United States v. Scheffer , and countless state and federal deci-. Polygraphs fit the pattern of many forensic scientific fields, being of concern to the courts, government agencies and law enforcement, but largely ignored by the scientific community.
A recent decision found the same to be true for fingerprinting United States v. Plaza, Although the district court subsequently vacated this decision and admitted the evidence, the judge repeated his initial finding that fingerprinting had not been tested and was only generally accepted within a discrete and insular group of professionals.
Hines [] on handwriting analysis and the more general discussion in Faigman et al. The lack of data on regularly used scientific evidence appears to be a systemic problem and, at least partly, a product of the historical divide between law and science. Federal courts only recently began inquiring directly into the validity or reliability of proffered scientific evidence.
Until , the prevailing standard of admissibility was the general acceptance test first articulated in Frye v. United States in Using that test, courts queried whether the basis for proffered expert opinion is generally accepted in the particular field from which it comes. In Daubert v. Merrell Dow Pharmaceuticals, Inc. Supreme Court held that Frye does not apply in federal courts. Under the Daubert test, judges must determine whether the basis for proffered expertise is, more likely than not, valid.
The basic difference between Frye and Daubert is one of perspective: courts using Frye are deferential to the particular fields generating the expertise, whereas Daubert places the burden on the courts to evaluate the scientific validity of the expert opinion. This difference of perspective has begun to significantly change the reception of the scientific approach in the court-room.
The polygraph is not unusual in this regard. In fact, topics such as bite mark and hair identification, fingerprinting, arson investigation, and tool mark analysis have a less extensive record of research on accuracy than does polygraph testing. Historically, the courts relied on experts in sundry fields in which the basis for the expert opinion is primarily assertion rather than scientific testing and in which the value of the expertise is measured by effectiveness in court rather than scientific demonstration of accuracy or validity.
These observations raise several issues worthy of consideration. First, if the polygraph compares well with other forensic sciences, should it not receive due recognition for its relative success? Second, most forensic sciences are used solely in judicial contexts, while the polygraph is also used in employment screening: Do the different contexts in which the technique is used affect the determination of its usefulness?
And third, since mainstream scientists have largely ignored forensic science, how could this situation be changed? We consider these matters in turn. Without question, DNA profiling provides the model of cooperation between science and the law. The technology was founded on basic science, and much of the early debate engaged a number of leading figures in the scientific community.
Rapidly improving technology and expanded laboratory attention led to improvements in the quality of the data and the strengths of the inferences that could be drawn. Even then, however, there were controversies regarding the statistical inferences National Research Council, , a. Nonetheless, from the start, judges understood the need to learn the basic science behind the technology and, albeit with certain exceptions, largely mastered both the biology and the statistics underlying the evidence.
At the same time, DNA profiling might be somewhat misleading as a model for the admissibility of scientific evidence. Although some of the forensic sciences, such as fingerprinting see Cole, , started as science, most have existed for many decades outside mainstream science. In fact, many forensic sciences had their start well outside the scientific mainstream. Moreover, although essentially probabilistic, DNA profiling today produces almost certain conclusions—if a sufficient set of DNA characteristics is measured, the resulting DNA profiles can be expected to be unique, with a probability of error of one in billions or less except for identical twins National Research Council, a.
In fact, the one. The accuracy of polygraph testing does not come anywhere near what DNA analysis can achieve. Nevertheless, polygraph researchers have produced considerable data concerning polygraph validity see Chapters 4 and 5. However, most of this research is laboratory research, so that the generalizability of the research to field settings remains uncertain.
The field studies that have been carried out also have serious limitations see Chapter 4. Moreover, there is virtually no standardization of protocols; the polygraph tests conducted in the field depend greatly on the presumed skill of individual examiners. Thus, even if laboratory-based estimates of criterion validity are accurate, the implications for any particular field polygraph test are uncertain.
Without the further development of standardized polygraph testing techniques, the gulf between laboratory validity studies and inferences about field polygraph tests will remain wide. The ambiguity surrounding the validity of field polygraphs is complicated still further by the structure of polygraph testing. Because in practice the polygraph is used as a combination of lie detector and interrogation prop, the examiner typically is privy to information regarding the examinee.
Thus, high validity for laboratory testing might again not be indicative of the validity of polygraphs given in the field. The usefulness of polygraph test results depends on the context of the test and the consequences that follow its use. Validity is not something that courts can assess in a vacuum.
The wisdom of applying any science depends on both the test itself and the application contemplated. A principal consideration in the applied sciences concerns the content of a test: what it does, or can be designed to, test. Concealed information polygraph tests, for example, have limited usefulness as a screening device simply because examiners usually cannot create specific questions.
There may be exceptions, as in some focused screening applications, as discussed above. Similarly, the import of the test itself must be considered. For instance, in the judicial context, the concealed information test format might present less concern than the comparison question format, even if they have comparable accuracy. Like a fingerprint found on the murder weapon, knowledge of the scene and, possibly, the circumstances of the crime, is at least one inferential step away from the conclusion that the subject committed the crime.
With this test, such an expert opinion would go directly to the credibility of the examinee and thus his or her culpability for the event in question. This possibility raises still another concern for courts, the possibility that the expert will invade the province of the fact finder.
As a practical matter, however, witnesses, and especially experts, regularly comment on the probable veracity of other witnesses, though almost never directly.
The line between saying that a witness cannot be believed and that what the witness has said is not believable, is not a bright line. Courts, in practice, regularly permit experts to tread on credibility matters, especially psychological experts in such areas as repressed memories, post-traumatic stress disorder, and syndromes ranging from the battered woman syndrome to rape trauma syndrome.
This issue is a policy consideration that must be made on the basis of understanding the science well enough to appreciate the quantity of error, and judgment about the qualitative consequences of errors the above discussion of errors and tradeoffs is thus relevant to considerations likely to face a court operating under the Daubert rule.
With most forensic science procedures, the criterion is clear. The value of fingerprinting, handwriting identification, firearms identification, and bite marks is closely associated with their ability to accomplish the task of identification. This is a relatively straightforward assessment. Polygraph tests, however, have been advocated variously as lie detectors and as aids for interrogation. They might indeed be effective for one or the other, or even both.
However, these hypotheses have to be separated for purposes of study. For purposes of science policy, policy makers should be clear about for which use they are approving—or disapproving—polygraphs. Courts have been decidedly more ambivalent toward polygraphs than the other branches of government.
Courts do not need lie detectors, since juries already serve this function, a role that is constitutionally mandated. Many policy makers, lawyers, and judges have little training in science.
Moreover, science is not a significant part of the law school curriculum and is not included on state bar exams. Criminal law classes, for the most part, do not cover forensic science or psychological syndromes, and torts classes do not discuss toxicology or epidemiology in analyzing toxic tort cases or product liability. Most law schools do not offer, much less require, basic classes on statistics or research methodology. In this respect, the law school curriculum has changed little in a century or more.
The general acceptance test of admissibility enunciated in the Frye decision expects little scientific sophistication of lawyers or judges. To understand how a rotor machine works, first recall the basic goal of cryptography: substituting each of the letters in a message, called plaintext, with other letters in order to produce an unreadable message, called ciphertext. It's not enough to make the same substitution every time—replacing every F with a Q , for example, and every K with an H.
Such a monoalphabetic cipher would be easily solved. A simple cipher machine, such as the Enigma machine used by the German Army during World War II, has three rotors, each with 26 positions.
Each position corresponds to a letter of the alphabet. Electric current enters at a position on one side of the first rotor, corresponding to a letter, say T.
The current travels through two other rotors in the same way and then, finally, exits the third rotor at a position that corresponds to a different letter, say R.
So in this case, the letter T has been encrypted as R. The next time the operator strikes a key, one or more of the rotors move with respect to one another, so the next letter is encrypted with an entirely different set of permutations. In the Enigma cipher machines [below] a plugboard added a fixed scramble to the encipherment of the rotors, swapping up to 13 letter pairs.
A rotor machine gets around that problem using—you guessed it—rotors. Start with a round disk that's roughly the diameter of a hockey puck, but thinner. On both sides of the disk, spaced evenly around the edge, are 26 metal contacts, each corresponding to a letter of the English alphabet.
Inside the disk are wires connecting a contact on one side of the disk to a different one on the other side. The disk is connected electrically to a typewriter-like keyboard. When a user hits a key on the keyboard, say W , electric current flows to the W position on one side of the rotor. The current goes through a wire in the rotor and comes out at another position, say L.
However, after that keystroke, the rotor rotates one or more positions. So the next time the user hits the W key, the letter will be encrypted not as L but rather as some other letter. Though more challenging than simple substitution, such a basic, one-rotor machine would be child's play for a trained cryptanalyst to solve.
So rotor machines used multiple rotors. Versions of the Enigma, for example, had either three rotors or four. In operation, each rotor moved at varying intervals with respect to the others: A keystroke could move one rotor or two, or all of them. Operators further complicated the encryption scheme by choosing from an assortment of rotors, each wired differently, to insert in their machine.
Military Enigma machines also had a plugboard, which swapped specific pairs of letters both at the keyboard input and at the output lamps. The rotor-machine era finally ended around , with the advent of electronic and software encryption, although a Soviet rotor machine called Fialka was deployed well into the s.
The HX pushed the envelope of cryptography. For starters it has a bank of nine removable rotors. The unit I acquired has a cast-aluminum base, a power supply, a motor drive, a mechanical keyboard, and a paper-tape printer designed to display both the input text and either the enciphered or deciphered text. In encryption mode, the operator types in the plaintext, and the encrypted message is printed out on the paper tape.
Each plaintext letter typed into the keyboard is scrambled according to the many permutations of the rotor bank and modificator to yield the ciphertext letter. In decryption mode, the process is reversed. The user types in the encrypted message, and both the original and decrypted message are printed, character by character and side by side, on the paper tape. While encrypting or decrypting a message, the HX prints both the original and the encrypted message on paper tape.
The blue wheels are made of an absorbent foam that soaks up ink and applies it to the embossed print wheels. Beneath the nine rotors on the HX are nine keys that unlock each rotor to set the initial rotor position before starting a message. That initial position is an important component of the cryptographic key. To begin encrypting a message, you select nine rotors out of 12 and set up the rotor pins that determine the stepping motion of the rotors relative to one another. Then you place the rotors in the machine in a specific order from right to left, and set each rotor in a specific starting position.
Finally, you set each of the 41 modificator switches to a previously determined position. To decrypt the message, those same rotors and settings, along with those of the modificator, must be re-created in the receiver's identical machine. All of these positions, wirings, and settings of the rotors and of the modificator are collectively known as the key. The HX includes, in addition to the hand crank, a nickel-cadmium battery to run the rotor circuit and printer if no mains power is available.
A volt DC linear power supply runs the motor and printer and charges the battery. The precision volt motor runs continuously, driving the rotors and the printer shaft through a reduction gear and a clutch. Pressing a key on the keyboard releases a mechanical stop, so the gear drive propels the machine through a single cycle, turning the shaft, which advances the rotors and prints a character.
The printer has two embossed alphabet wheels, which rotate on each keystroke and are stopped at the desired letter by four solenoids and ratchet mechanisms. Fed by output from the rotor bank and keyboard, mechanical shaft encoders sense the position of the alphabet printing wheels and stop the rotation at the required letter.
Each alphabet wheel has its own encoder. One set prints the input on the left half of the paper tape; the other prints the output on the right side of the tape. After an alphabet wheel is stopped, a cam releases a print hammer, which strikes the paper tape against the embossed letter. At the last step the motor advances the paper tape, completing the cycle, and the machine is ready for the next letter.
As I began restoring the HX, I quickly realized the scope of the challenge. The plastic gears and rubber parts had deteriorated, to the point where the mechanical stress of motor-driven operation could easily destroy them. Replacement parts don't exist, so I had to build such parts myself. After cleaning and lubricating the machine, I struck a few keys on the keyboard. I was delighted to see that all nine cipher rotors turned and the machine printed a few characters on the paper tape.
But the printout was intermittently blank and distorted. I replaced the corroded nickel-cadmium battery and rewired the power transformer, then gradually applied AC power. To my amazement, the motor, rotors, and the printer worked for a few keystrokes. But suddenly there was a crash of gnashing gears, and broken plastic bits flew out of the machine.
Printing stopped altogether, and my heartbeat nearly did too. I decided to disassemble the HX into modules: The rotor bank lifted off, then the printer. The base contains the keyboard, power supply, and controls. These snubbers had disintegrated. Also, the foam disks that ink the alphabet wheels were decomposing, and gooey bits were clogging the alphabet wheels. I made some happy, serendipitous finds. To rebuild the broken printer parts, I needed a dense rubber tube.
I discovered that a widely available neoprene vacuum hose worked perfectly. Using a drill press and a steel rod as a mandrel, I cut the hose into precise, millimeter sections. But the space deep within the printer, where the plastic snubbers are supposed to be, was blocked by many shafts and levers, which seemed too risky to remove and replace.
So I used right-angle long-nosed pliers and dental tools to maneuver the new snubbers under the mechanism. After hours of deft surgery, I managed to install the snubbers. The HX has nine rotors and also uses a technique called reinjection. Each rotor has a set of conductors that connect each and every electrical contact on one side of the rotor with a different contact on the other side. For every rotor the pattern of these connections is unique. When the operator strikes a key on the keyboard, representing one of 26 letters, current travels through the set of nine rotors twice, once in each direction, and then through a separate set of 15 rotor contacts at least two times.
This reinjection technique greatly increases the complexity of the cipher. The ink wheels were made of an unusual porous foam. I tested many replacement materials, settling finally on a dense blue foam cylinder.
Alas, it had a smooth, closed-cell surface that would not absorb ink, so I abraded the surface with rough sandpaper. After a few more such fixes, I faced just one more snafu: a bad paper-tape jam. I had loaded a new roll of paper tape, but I did not realize that this roll had a slightly smaller core. The tape seized, tore, and jammed under the alphabet wheels, deeply buried and inaccessible.
I was stymied—but then made a wonderful discovery. The HX came with thin stainless-steel strips with serrated edges designed specifically to extract jammed paper tape.
I finally cleared the jam, and the restoration was complete. One of the reasons why the HX was so fiendishly secure was a technique called reinjection, which increased its security exponentially. Rotors typically have a position for each letter of the alphabet they're designed to encrypt.
So a typical rotor for English would have 26 positions. But the HX's rotors have 41 positions. That's because reinjection also called reentry uses extra circuit paths beyond those for the letters of the alphabet.
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