The RISKS Digest
Volume 5 Issue 66

Friday, 27th November 1987

Forum on Risks to the Public in Computers and Related Systems

ACM Committee on Computers and Public Policy, Peter G. Neumann, moderator

Please try the URL privacy information feature enabled by clicking the flashlight icon above. This will reveal two icons after each link the body of the digest. The shield takes you to a breakdown of Terms of Service for the site - however only a small number of sites are covered at the moment. The flashlight take you to an analysis of the various trackers etc. that the linked site delivers. Please let the website maintainer know if you find this useful or not. As a RISKS reader, you will probably not be surprised by what is revealed…


Mariner I
Eric Roberts
FORTRAN pitfalls
Jim Duncan
PIN verification
Otto J. Makela
Sudden acceleration revisited
Leslie Burkholder
Re: CB radio and power
Maj. Doug Hardie
An earlier train crash — Farnley Junction
Clive D.W. Feather
Info on RISKS (comp.risks)

Mariner I

Eric Roberts <roberts@src.DEC.COM>
Wed, 25 Nov 87 18:33:14 pst
When Steve Berlin and I were writing the chapter on SDI for the new CPSR
book _Computers in Battle_ (Boston: Harcourt Brace Jovanovich, 1987), I
tried to track down a more complete reference to the Mariner I story.
The theory that this was due to the substitution of a period for a comma
in a FORTRAN DO statement seems to stem initially from the following
quote from G.J.Meyers, _Software Reliability: Principles and Practice_
(New York: John Wiley, 1976):

      In a FORTRAN program controlling the United States' first
      mission to Venus, a programmer coded a DO statement in a
      form similar to the following:

                             DO 3 I = 1.3P

      The mistake he made was coding a period instead of a comma.
      However, the compiler treated this as an acceptable
      assignment statement because FORTRAN has no reserved words,
      blanks are ignored, and variables do not have to be
      explicitly declared.  Although the statement is obviously an
      invalid DO statement, the compiler interpreted it as setting
      a new variable DO3I equal to 1.3.  This "trivial" error
      resulted in the failure of the mission.  Of course, part of
      the responsibility for this billion-dollar error falls on
      the programmer and test personnel, but is not the design of
      the FORTRAN language also partially to blame?

Unfortunately, Meyers lists no references for this version of history.
Some years ago, as part of the background work for the slide show
_Reliability and Risk_, Steve Berlin had called to ask about sources for
this story.  Meyers could not remember an exact source.

Since this much tracing left me without a definitive source, I checked
the _New York Times_ index and _Readers' Guide_ indices for 1962.  The
most informative article appeared in the _New York Times_ of Saturday,
July 28--six days after the aborted launch:

                           For Want of Hyphen
                          Venus Rocket Is Lost

                            By GLADWIN HILL
                     Special to the New York Times

         LOS ANGELES, July 27--The omission of a hyphen in some
      mathematical data caused the $18,500,000 failure of a
      spacecraft launched toward Venus last Sunday, scientists
      disclosed today.
         The spacecraft, Mariner I, veered off course about four
      minutes after its launching from Cape Canaveral, Fla., and
      had to be blown up in the air.
         The error was discovered here this week in analytical
      conferences of scientists and engineers of the National
      Aeronautics and Space Administration, the Air Force and the
      California Institute of Technology Jet Propulsion
      Laboratory, manager of the project for N.A.S.A.
         Another launching will be attempted some time in August.
      Plans had been suspended pending discovery of what went
      wrong with the first firing.
         The hyphen, a spokesman for the laboratory explained, was
      a symbol that should have been fed into a computer, along
      with a mass of other coded mathematical instructions.  The
      first phase of the rocket's flight was controlled by radio
      signals based on this computer's calculations.
         The rocket started out perfectly on course, it was
      stated.  But the inadvertent omission of the hyphen from the
      computer's instructions caused the computer to transmit
      incorrect signals to the spacecraft....

The first paragraph makes it sound as if this might be a data entry
error and not a coding error at all.  Later paragraphs, however,
indicate that this was part of the "coded mathematical instructions."
Other references to the Mariner I failure appear in the letters section
of the _New York Times_ of August 2 (page 24) and in the August 6 issue
of _Newsweek_ (page 75) and seem to corroborate the view that this was a
programming error.

This account agrees with the recent report from Henry Spencer (RISKS-5.64)
who cites "Far Travellers" by Oran W. Nicks.  On the whole, this explanation
seems to have more documentary evidence than the FORTRAN version of the story 
presented by Meyers.  The existence of other overstatements in his account
(in particular, $18,500,000 << $1,000,000,000) also reduces its credibility.

Of course, the FORTRAN version of the story has received widespread
distribution of late (it is, after all, a lovely story), including citations in

   o  Jim Horning, "Note on Program Reliability," _Software
      Engineering Notes_, 4:4, October 1979, p. 6.
   o  Peter Neumann, "Letter from the Editor," _Software Engineering
      Notes_, 8:5, October 1983, p. 4 (credited to David Smith of
      CMU, who heard it from his instructor in 1970 or 1971).
   o  H.S. Tropp, "Fortran Anecdotes," _Annals of the History of
      Computing_, 6:1, January 1984, p. 61.
   o  Peter Neumann, "Risks to the Public," _Software Engineering
      Notes_, 11:5, October 1986, p. 17.

However, unless there is more definitive evidence to support this, I
think it must be regarded as apocryphal.

My own solution in _Computers in Battle_ was to write:

      Shortly after its launch on July 22, 1962, the Mariner I
      Venus probe veered off course and had to be destroyed by
      mission control officials.  The problem was later traced to
      a single character error in the controlling software.

This covers both explanations and seems to be on relatively safe ground.

                                   [Yes, but it bugs the question.  PGN]

FORTRAN pitfalls (Re: RISKS-5.63)

Jim Duncan <>
Thu, 26 Nov 87 13:40:20 EST
(Regarding the DO ... I=1.3 problem:)

I too have heard this `story' many times, and each time the space vehicle took
on a new name, and it was on its way to a different planet or mission.  The
text I am reading for a course in principles of programming languages is the
first place I have seen this incident documented.  The author is discussing
the design of syntactic structures in FORTRAN and the unfortunate effects of
adopting a lexical convention that caused blanks to be ignored everywhere:

  "In FORTRAN, the statement

    DIMENSION IN DATA (10000), RESULT (8000)

  is exactly equivalent to


  and, for that matter,

    D I M E N S I O N IN DATA (10000), RESULT (8000)

  While this may seem to be a harmless convenience, in fact it can cause
  serious problems for both compilers and human readers.  Consider this legal
  FORTRAN statement:

    DO 20 I = 1.100

  which looks remarkably like the DO-statement:

    DO 20 I = 1,100

  In fact, it is an assignment statement of the number 1.100 to a variable
  called `DO20I', which we can see by rearranging the blanks:

    DO20I = 1.100

  You will probably say that no programmer would ever call a variable `DO20I',
  and that is correct.  But suppose the programmer _intended_ to type the
  DO-statement above but accidentally types a period instead of a comma (they
  are next to each other on the keyboard).  The statement will have been
  transformed into an assignment to `DO20I'.  The programmer will probably not
  notice the error because `,' and `.' look so much alike.  In fact, there will
  be no clue that an error has been made because, conveniently, the variable
  `DO20I' will be automatically declared.  If you think things like this can't
  happen, you will be surprised to learn that an American Viking Venus probe
  was lost because of precisely this error."

The above is from Bruce J. MacLennan, _Principles_of_Programming_Languages_
(second edition), CBS College Publishing, 1987, pp. 89-90.  Mr. MacLennan goes
on to elaborate on the principles of good language design violated by FORTRAN,
such as Defense in Depth.

To add my two-cents worth:  When I first heard the Viking story, I inferred
that the offending DO-statement was in the code which either positioned the
navigational motors, or did the navigation calculations.  I was told that the
launch went perfectly and the probe reached the desired earth orbit.  When the
probe fired its motors to leave earth orbit, however, it supposedly rolled
over on its back, fired in the wrong direction, and promptly _disappeared_
from all tracking systems.  No one knows where the hell it went....

Jim Duncan, Computer Science Dept, Old Dominion Univ, Norfolk VA 23529-0162
(804)440-3915     INET:    UUCP: ...!sun!xanth!jim

PIN verification

Thu, 26 Nov 87 13:11 O
In RISKS 5.61, John Pershing <> writes:
  >I cannot speak for *all* ATM and POS systems, but the major banks
  >generally know what they are doing with respect to PIN security.  The PIN
  >number is *not* stored on your ATM card — it is stored in your bank's
  >database and, possibly, in one or more interbank clearinghouses.  This
  >makes it possible to have your PIN changed without getting the card
  >re-magnetized (assuming your bank has it's act together).  Note that your
  >account number probably isn't even written on the card — only a number
  >that identifies that particular card. [...]
  >John A. Pershing Jr., IBM, Yorktown Heights

Well, it *would* seem that the Finnish banks use a different system.  Perhaps
I should first describe the most common types of plastics we have here:

* the autoteller cards, that can only be used in ATM's
* the "Bank Cards", that work at ATM's and can be used for buying stuff;
  using them is legally the same as writing out a cheque for the same amount
* the VISA-combocard, that is a combined ATM/Bank Card/VISA-card; when you
  use them for buying stuff you have to tell what you want it to be used as

All the abovementioned cards DO have the attached account number on them.
It is possible also to have SEVERAL accounts on them, but I'm not sure how
this is accomplished.  This option is only offered by one bank, so it might
be just their hack.

Follows a paragraph from the official guide to implementing off-line
POS terminals using magnetic card identification:

        PIN-verification is done by the Security Unit, which is connected
        to the POS terminal, according to the the PVV-number, which is read
        off the magnetic stripe of the card.  The requirements for PIN-
        verification are given separately in "POS terminal security standards".
        Written requests for the distribution of these standards may be sent
        to AIP-security Chief Lars Anrkil, SKOP (Kilo), PL 400, 00101

[SKOP is a big Finnish banking group, more or less a "collection of competing
fiefdoms", as David G. Grubbs <dgg@dandelion.CI.COM> put it in RISKS 5.61;
it would seem that the Finnish Banking Association has given them the job of
maintaining and distributing these security standards.]

Here's a few arguments against the systems working by being on-line to the
bank computer or some other similar system:

* the guide was for OFF-LINE POS terminals.
* the same PIN-numbers are used internationally, in VISA-card -based ATM-type
  machines, where you use your VISA-combocard to get money that will be billed
  in your next VISA bill.  I have difficulties believing that even in this
  information age they would maintain a computer link from all over the world
  to remote Finland :-)
* I have several times went to an ATM that is used by several banks in co-
  operation, inserted my card, typed in my PIN and received a message saying
  "Your bank's computer is down".  The PIN was verified BEFORE the ATM tried
  to contact my bank's computer.
* I have asked several times if it is possible to change my card's PIN number
  (just to know if it is possible), and have always received a reply stating
  "no, it's not possible, it's derived from your card number".  This is very
  weak, since bank people generally aren't that good on technical aspects...

I think these taken together are pretty strong indications that the PIN
verification CAN be done off-line, at least for the Finnish standard of cards.

I dearly do hope that security in these systems is not maintained by secrecy
ONLY!  However, I have had the company I work in part-time order the set of
security standards, so as soon as we get them, I'll let you people know more...

Otto J. Makela, U of Jyvaskyla
Mail: Kauppakatu 1 B 18, SF-40100 Jyvaskyla, Finland
Phone: +358 41 613 847
BBS: +358 41 211 562 (V.22bis/V.22/Bell 212A/V.21)

Sudden acceleration revisited

Leslie Burkholder <>
Thu, 26 Nov 87 13:15:59 -0500 (EST)
Honda motor company has offered replacements for the chip controlling
acceleration in the 88 Civic. Some people have complained of problems with
this chip in their Civics.

Re: CB radio and power (RISKS-5.64)

"Maj. Doug Hardie" <Hardie@DOCKMASTER.ARPA>
Wed, 25 Nov 87 11:44 EST
[For the record.  Truth-in-harmonics department.]

  > The second harmonic of 26-27 Mhz signals rounds out to 104-108 Mhz, 
  > or the upper half of commercial FM radio.  [Jeffrey R Kell.  RISKS-5.64]

According to my understanding of the new-new-math (I am a product of the new
math), that would have to be the fourth harmonic.
                                                         — Doug

               [I hope no one pleads the fifth.  130-135 would sound 
               suspiciously like late Beethoven String Quartets.  
               Gesunta-heit.  PGN]

An earlier train crash — Farnley Junction

"Clive D.W. Feather" <mcvax!!cdwf@uunet.UU.NET>
27 Nov 87 16:48:37 GMT
Not quite computers, but after the item in RISKS-5.64 about the Swedish
train crash, readers might find this interesting.

Summary of official report on accident at Farnley Junction (Yorkshire)
in 1977, on British Railways.

Farnley Junction is a few miles from Leeds Signal Box, and is remotely
controlled from there. All safety interlocking logic is in the signal
box itself (all signalling in this area is carried out by 12V relay
logic). The distance is such that an intermediate repeater unit repeats
all relay signals between the junction and the box.

The physical layout is as follows:

        Little used  \
        branch line   \
                     S          \
      --->-----------------------*------*------------->--- Up line
      ---<--------------------------------*-----------<--- Down line
   * = points, S = signal

Normal logic, e.g., for signals, is binary, but the controls and position
detection of the up-to-down-line crossover happened to be trinary (line A
positive = straight ahead, line B positive = cross over, neither positive
= no command / not correctly set).

On the day in question, a fault at the repeater unit was causing problems.
Both signals were set to Danger by the signalman, and an engineering team
then changed the rectifier in the power supply at the repeater unit.

The loss of power caused the main signalling logic to believe the crossover
was not correctly set (no repeat of the detection), and so it set the control
lines to drive the crossover back to the stright ahead position (this will
stay driven until the detection is correct - meantime, the signals are locked
at Danger).

Trains came to a halt at both signals.

The engineers restored power to the repeater, but had wired in the rectifier
the wrong way round. This had the effect of reversing the polarity of voltages
repeated - not important for binary signals.The crossover took the incoming
voltage as a command to move to the "crossover" position, and did so.
The detection mechanism correctly reported "crossover" - this was reversed
at the repeater, and the main signalling logic (correctly) took the incoming
signal to mean that the points were locked in the "straight ahead" position.

The signalman now set both signals to Proceed, and the signalling logic
allowed him to do so. The train on the Up line started off immediately
(the other driver was trying to figure out why the points were set the
wrong way !), traversed the crossover, and collided with the train on the
Down line, killing two people.

I know this isn't computing, but there's a lesson in it, even so.

         [Don't lessen the lesson by thinking this isn't computing.
         Circuitry, programs, algorithms, and people have much in common.  PGN]

Please report problems with the web pages to the maintainer