Creating A Subpoena-Proof
Diary: A Technological Solution to A Legal Problem
James D Miller
Assistant Professor of
Smith College, USA
Associate Professor of Computer
Smith College, USA
Many high ranking government
officials are afraid to keep a diary because of the possibility
that it will be subpoenaed. This will undoubtedly be a great loss
to future historians. This paper describes a method by which a
subpoena-proof diary can be kept. The diary can be encrypted in a
way such that no one, not even the author, can read it until some
period of time has elapsed. In this way, the diary can be read by
future historians but not by contemporary political
JIM LEHRER: 'Are you keeping a
diary? Are you keeping good notes on what's happening?'
HILLARY CLINTON: 'Heavens no! It
would get subpoenaed. I can't write anything down
[Laughing]'[ 1 ].
Privacy, Unraveling, Subpoena and Diary
This is a Refereed
article published on 31 October 2001.
Citation : Miller, J
and Gao, L, 'Creating A Subpoena-Proof Diary: A Technological
Solution to A Legal Problem', Refereed article, 2001 (3) The Journal of Information, Law and Technology
<http://elj.warwick.ac.uk/jilt/01-3/miller.html>. New citation as at 1/1/04:
Many current and former
high-ranking government officials have said that they would not
keep a diary because of fear that it would be subpoenaed[ 2 ]. Fear of a prosecutor
with subpoena power is likely to prevent any future American
president from keeping a reasonably complete diary unless a method
can be devised to keep diaries secure. This paper suggests that
authors can use computer encryption to create subpoena-proof
Computer encryption converts a
plain text into a coded data file. The coded data file can be
decrypted (turned back into a plain text) only by someone who has
the encryption key. The encryption key is simply a number.
Encryption permits a diary's author to prevent anyone from reading
the diary who does not have the encryption key. However, if the
author had the key, the diary would not be subpoena-proof because
the subpoenaing party can demand the key, and the author would
under some circumstances be legally obligated to reveal it. The
only way that encryption could protect the author would be if no
one, not even the author, has the encryption key. Therefore, to
create a subpoena-proof diary, an author should encrypt her diary
and throw away the encryption key. But then, how could the diary
ever be read?
Before the author throws away the
encryption key, she can perform a mathematical operation on the
encryption key which produces a new number. While this new number
cannot be used directly to decrypt the diary, the original key can
be recovered using this new number. However, recovering the
original key from this new number would take a considerable amount
of time. The mathematical operation determines the amount of time
it would take to recover the original encryption key from the new
number. Depending on the mathematical operation used, recovering
the original encryption key could take days, years or decades.
During the period it would take to recover the original encryption
key, the diary would be completely subpoena-proof. This method
would be very useful to a president who does not want her diary to
be read until after she leaves office.
The encryption scheme this paper
proposes takes advantage of the continual increase in computer
speeds. Because of the future expected increases in computer
speeds, an encryption key that would take several years to recover
today could be recovered in only a few months ten years from
One might think that a flaw with
any subpoena-proofing method based on encryption lies in the fact
that a special prosecutor or congressional committee could quickly
decrypt the diary by using millions of computers coordinated via
the Internet. However, under the scheme described in this paper,
using multiple computers would not accelerate the recovery of the
data file. The speed at which a file can be recovered is solely a
function of the speed of the single fastest available
computer[ 3 ].
Another flaw with any encryption
technology is that a data file that is safe today may not be safe
in the future if there is faster than expected increase in computer
speeds. However, the scheme this paper proposes allows the author
to strengthen the diary's security at any time during which the
diary is not under subpoena.
In Section I, this paper examines
why diaries are not secure. The section explores why the Fourth and
Fifth Amendments do not always protect a diary from subpoenas and
why the logic of game theory might effectively force a politician
to reveal her diary even if she is not legally required to do so.
Section II explains how encryption works in general and describes
an encryption scheme for keeping a subpoena-proof diary. The
Appendix provides a detailed technical explanation of the
Section I. Why Diaries Are Not Secure
2.1 Fifth Amendment Protection
The Fifth Amendment to the United
States Constitution provides in part that no person 'shall be
compelled in any criminal case to be a witness against himself'.
The United States Supreme Court used to hold that this prevented a
court or prosecutor from compelling a person to release documents
that she prepared. Recently, the Supreme Court ruled that the Fifth
Amendment does not bar the forced release of non-personal papers.
The Supreme Court has never decided whether the Fifth Amendment
prevents the forced revelation of personal papers. The federal
appeals courts are split on this issue[ 4 ].
In Boyd v. United States[ 5 ], a district attorney
forced a business to turn over invoices that the business created.
These invoices were then used as evidence against the business. The
Supreme Court held that compelling an owner to produce private
books or papers is the equivalent to:
'compelling him to be a witness
against himself, within the meaning of the Fifth Amendment to the
Constitution'[ 6 ].
Had the Supreme Court not modified
Boyd in subsequent opinions, then authors of diaries could never be
compelled to reveal them.
In Fisher v. United States[
7 ], the Supreme Court
significantly limited the Fifth Amendment protection against the
forced revelation of papers and documents. In Fisher, the Court
held that forcing an individual to produce work papers does not
violate the Fifth Amendment because:
'it does not compel oral testimony;
nor would it ordinarily compel the taxpayer to restate, repeat, or
affirm the truth of the contents of the documents sought'[
However, the Court explicitly wrote
that their opinion does not apply to private papers, leaving open
the question of whether an individual could be compelled to turn
over a diary[ 9 ].
In an concurring opinion in United
States v. Doe, Justice O'Connor wrote that the Fifth Amendment
provides no protection for 'private papers of any kind'[ 10 ]. However, in a
dissenting opinion in that same case, Justice Marshall wrote that
he viewed the Court's ruling as not limiting the Fifth Amendment's
protection for private papers. Thus, the Supreme Court has never
clearly determined whether the Fifth Amendment provides protection
The circuit courts are currently
divided over whether the Fifth Amendment provides any protection
for personal papers[ 11 ]. A
District Court in the District of Columbia recently held that the
Fifth Amendment did not offer protection for a senator who wished
to prevent a senate committee from subpoenaing his diary[ 12 ]. Thus, it is unlikely
that a federal government official would be able to use the Fifth
Amendment to stop a congressional committee or a special prosecutor
from obtaining her diary.
2.2 Fourth Amendment
The Fourth Amendment reads in part
that 'The right of the people to be secure in their persons,
houses, papers, and effects against unreasonable searches and
seizures shall not be violated.' As with the Fifth Amendment, the
Fourth Amendment used to provide strong protection for individual's
diaries but no longer does so[ 13 ].
The Supreme Court previously held
that the government could seize only the instrumentalities or the
fruits of crimes[ 14 ].
The Court also used to hold that the Fourth Amendment did not allow
private papers to be seized if there were mere evidence of a
crime[ 15 ]. In Warden v.
Hayden[ 16 ], the Court reduced
Fourth Amendment protections and held that there was no greater
Fourth Amendment protection for evidence of crimes than for the
instrumentalities or fruits of crimes. Consequently, under current
constitutional doctrine, the Fourth Amendment does not protect an
individual from having her diary taken if the government has a
reasonable justification for believing that it contains evidence of
2.3 Effective Disclosure and Game
Even if an author can be confident
that her diary will never be read without her permission, she might
still be reluctant to keep a diary. This is because if it is known
that she is keeping a diary, not releasing it can be politically
costly due to a concept in game theory known as unraveling[
17 ]. Unraveling can
effectively force an author to release the contents of her
Imagine a situation where a
President is in serious political trouble. She is accused of doing
something which, if true, could lead to her impeachment. Assume
that it is known that she has kept a detailed diary while in
office, and that the opposition party is calling for the President
to release her diary. Further imagine that the benefit or harm of
the contents of the diary can be ranked on a scale from 1 to 5. The
higher the number, the less harmful the information is to the
President. Assume that people believe that the contents are equally
likely to take on any value between 1 and 5, and that on average
the contents rank a value of 3. If the President has a chance to
release the diary and does not, people will reasonably believe that
the contents do not rank a 4 or 5. This is because if people
initially believe that the diary, on average, ranked a 3, but the
President knows that it ranked higher, the President will surely
release the contents of the diary. Therefore, by not releasing the
contents of the diary, the President will send a signal that its
contents are not higher than 3. Now that everyone knows that the
diary does not rank higher than 3, people will assume that the
diary is equally likely to rank a 1, 2, or 3, and that on average,
people would believe that the diary would rank a 2. So, if the
diary really ranks a 3, the President will surely now release its
contents. If the President still refuses to release the contents of
the diary, people will assume that it does not rank higher than 2.
However, this would cause people to change their view about the
rank of the diary. People now might assume that since the rank is
not greater than 2, it is equally likely to be 1 or 2, and that on
average, the contents rank a value of 1.5. If people believe that
the average rank of the diary is 1.5, the President will surely
release the diary if its rank is really 2. Thus, if the President
does not release her diary, people will assume that it contains the
worst possible information.
One can see how unraveling can
force the President to reveal the contents of her diary if it does
not rank a 1. If the diary's contents do in fact rank a 1 and the
President does not reveal its contents, people will assume that it
ranks a 1[ 18 ].
Note that this situation is what game theorists call a stable
equilibrium. If people believe that the President will release the
contents of her diary unless they are ranked a 1, the President has
an incentive to release the contents unless they are indeed ranked
a 1. Thus, the individual's beliefs are consistent with the
As a result, a law prohibiting a
diary from being read without its author's permission might not be
enough to convince a high ranking government official to keep a
diary. The law would also have to forbid the author from releasing
the diary while in office, but such a law would clearly be
unconstitutional. The only solution to this problem is for it to be
known that the President lacks the ability to release the contents
of her diary.
Section II. The Encryption Solution
3.1 How Encryption Works
A typical encryption scheme works
as follows[ 19 ].
The plain text to be encrypted is transformed by a function that is
parameterized by a key. The output of the encryption process is a
coded text. A fundamental rule of cryptography is that one must
assume that the encryption function is known. The encryption key
is, however, typically kept secret. The person who knows the key
can recover the original text by using the key and the decryption
Since the real secrecy is in the
key, its length is a major design issue in an encryption scheme.
Similar to the principle of the combination lock, if the key is two
bits long, there are only 4 possibilities. The longer the key, the
less likely someone can find the key by exhaustively searching all
possible keys. In general, the number of possible for an n-bit key
is 2 n . Therefore, one needs a long key to
3.2 A Scheme to Create a Subpoena-Proof
This paper proposes that an author
use a standard encryption scheme to encrypt her diary. The
encryption scheme is called Data Encryption Standard (DES). DES
uses mathematical functions to effectively hide the original text
from someone who does not have the encryption key.
After the author has encrypted her
diary, she should use a mathematical process, which is described in
the appendix, to transform the encryption key. The transformed key
cannot be directly used to decrypt the plain text. However, it can
be used to recover the original encryption key.
The recovery of the encryption key
from the transformed key takes a considerable amount of time. The
author can choose the approximate amount of time it would take
anyone to recover the original encryption key from the transformed
key. The longer it takes to recover the encryption key, the more
secure the diary is.
The author needs to choose two
parameters: the amount of time she would like the diary to remain
secure for and the amount of time she is willing to wait before she
starts to recover the diary. These two parameters determine how
long it will take the author to recover the diary. (The Appendix describes the relationship between these three lengths
of time). For example, if the author wants to make her diary secure
for 8 years and is willing to wait 30 years (from the time at which
the diary was first encrypted) before she starts to recover the
diary, the recovery process will take approximately 4 hours. In
contrast, if she still wants to make her diary secure for 8 years
but only wants to wait 10 years before she starts to recover the
diary it will take her 9 months to recover the diary.
To find the encryption key under
most encryption schemes, one can conduct an exhaustive search for
all possible keys. Therefore, it would be helpful to use multiple
computers to search for the correct key. The scheme described in
this paper eliminates the benefit of using multiple computers to
recover the encryption key[ 20 ].
Moore's Law states that computer
speed doubles every eighteen months. This paper uses Moore's Law to
estimate the length of time a diary is secure. However, computer
speed might increase faster than Moore's Law estimates. To
circumvent this problem, this paper proposes a scheme that allows
the author to incrementally encrypt the diary at any future time.
For example, suppose that one year after the President has started
keeping and encrypting her diary, IBM perfects quantum computing
which causes computer speeds to increase tenfold. The security of
the President's diary will now be greatly reduced. However, the
President could overcome this problem by strengthening the diary's
encryption so that it becomes as secure as it was before IBM's
This paper proposes a practical
method by which a president or another government official can keep
a diary and be reasonably confident that no one can read it while
they are still in office. The longer the author is willing to wait
before anyone can read the diary and the more time that can be
devoted to decrypt the diary, the more secure the diary will be
while she is in office.
This appendix provides a detailed
technical description of how to create a subpoena- proof
Part A. Encrypting the
This paper describes an encryption
scheme for keeping a diary[ 21 ]. It then describes how to apply this scheme for a
Denote the diary by D and the
length of the time to keep the diary secret by T.
Generate a composite number n= pq,
where p and q are two large (e.g. 300-bit) randomly-chosen
Choose t to be the number of the
squaring module n operations that the computer can perform in time
Pick a random key K for a
conventional cryptosystem, such as Data Encryption Standard (DES).
This key should be long enough (e.g. 256 bits) so that searching
for it is infeasible, even with the advances in computer speed
expected within time T. Encrypt D with key K using DES encryption
algorithm: D k =DES(K, D)
Pick a random number a modulo n
(with 1<a<n), and compute K'=K a 2 t (mod
n). This step can be done efficiently by first computing
e=2 t (mod m) and then compute b=a e
Save n, a, t, K', D k . Discard the rest.
Part B. Decrypting the
Two known approaches to decrypt the
1. Find the DES key K by
exhaustively searching from all possible keys of 256
Since K is 256 bit long, searching
for it is infeasible even with the advances in computer speed
expected within time T.
2. Find the DES key K by using K'
b= a 2 t (mod n).
There are two known ways to compute
Compute m=(p-1)(q-1). Then compute
e= 2 t (mod m).
Finally, compute b= a e (mod n).
However, given n, finding m is
probably as hard as factoring n. Mathematicians have been trying to
factor large numbers for at least 3000 years and no efficient
algorithm has been found. For example, factoring a 600-digit number
requires 10 55 years of computer time assuming the best
known algorithm and a computer with 1- second instruction time. Even if
computers continue to get faster by an order of magnitude per
decade and we can use most of the computers in the Internet, it
will be centuries before factoring 600-bit number becomes
Compute b by starting with a and
sequentially performing squaring modulo n operation t
Therefore, approach 2(b) is the
only feasible way. Furthermore, by varying value t, we can control
the time that the diary D can be decrypted. This is because
repeated squaring seems to be an 'intrinsically sequential'
process. No one knows a way to parallelize it since each squaring
needs the result of the previous squaring. Having many computers is
no better than having one. Although having a fast computer is
better than having a slow one, the degree of variation in
computation speed of a single computer can be estimated in
accordance with the technology, while the computation speed of a
parallel computer or many computers on the Internet combined
depends on one's budget.
Part C. Choosing the
Parameter To Ensure the Desired Security
To ensure that the diary is secure
within 8 years and the diary can be recovered within 4 hours in 30
years, we need to choose t to satisfy the following
Condition 1. Within 8 years of the
presidency, no computer can decrypt the diary even if the president
Condition 2. It takes only 4 hours
to decrypt the diary using an average-speed computer after 30
To satisfy condition 1, one can
assume a high-speed computer and the computer cannot decrypt the
diary in 8 years time even if the computer is dedicated to
decrypting the diary. Suppose S i is the maximum number
of squaring module n operations that a high-speed computer can
perform in the ith year during the next 8 years.
Then t has to satisfy: , where one assumes that
the computer is upgraded every year for this purpose.
According to Moore's Law[ 22 ], the computer speed
doubles every 18 months. To be conservative, we assume that the
computer speed doubles every year, i.e., S i 1 =
2S i . Therefore, t>255 S 1.
To satisfy condition 2, one has to
ensure that an average-speed computer (30 years later) can decrypt
the diary within 4 hours. In other words, t <
S 30 /6/365 = S 30 /2190. According to the
Moore's Law, .
Therefore, t < 456 S 1 .
Therefore, we can choose t to be
between 255 S 1 and 456 S 1 . Note that we might
want to be conservative in estimating the increase of the
computational speed to ensure the timely recovery of the diary. In
the next section, we present the scheme to increase the security of
the diary when the computer speed is increased in at an unexpected
Part D. Incremental
If the computational speed
increases at an unexpected rate, the diary can be encrypted one or
more times to ensure its security within 8 years. This can be done
Choose a big t 1 that
ensures the diary's secrecy within 8 years according to the current
estimate and big enough key K 1 .
Perform the same mathematical
operation on K 1 using a large composite number
n 1 = p 1 q 1 and a 1 to get
K' 1 .
Note that p 1 and
q 1 are randomly-chosen large primes and a 1 is
a random number modulo n 1 .
Use K 1 to encrypt
D k . Save the encryption result as D k,,k1.
Save n, n 1, a, t, t 1 , K', K' 1,
To recover the diary, we first need
to find K 1 and then decrypt D k,,k1 to
D k . Finally, find K and then decrypt D k to D.
Note K and K 1 can be found in parallel. Therefore, the
time it takes to recover the diary can be controlled by
Such an incremental process can go
on as many times as needed, i.e. if computer speed increases
1 . The NewsHour With Jim
Lehrer, May 29, 1996.
2 . Dee Dee Myers, former
Clinton Press Secretary said 'People joke, Do you keep a diary?'
Are you kidding? It will be subpoenaed'. The problem is that that's
not really a joke. People you know, it'd be perfectly normal and
legitimate for somebody to want to keep a diary of an experience
like working at the White House, and spending time with the
president of the United States. People don't do that anymore'
(Nightline, ABC News, December 13, 1996). Harold Ickes, former
deputy chief of staff for the Clinton administration, said: 'I
regret what has--the way these Whitewater and other hearings have
come out because I was going to keep a diary for the last year but
after what happened to Joseph Steiner and others, I just said I am
not going to do it' (Larry King Live, CNN, November 21, 1997).
Senator Bob Packwood was forced to resign partly because of the
contents of his diary. Leon Penetta, former chief of staff of the
Clinton administration, said that a lesson from the Whitewater
hearings was never to keep a diary (Fox morning news, WTTG-TV
Washington, DC, August 8, 1994). Television commentator David
Brinkley said: 'No president should keep a diary' (The Week With
David Brinkley, ABC News, February 4, 1990). George Stephanopolous,
former high-ranking Clinton advisor, is consulting a memory
specialist to aid his writing a book about his White House
experience because he did not keep a diary since it would have been
subpoenaed (Media Week, A/S/M Communication June 23, 1997). Mike
McCurry, White House press secretary said that fear of subpoenas
has stopped most White House staffers from keeping diaries (Dallas
Morning News, March 8, 1998). Trent Lott, Senate Majority Leader
said that he does not keep a diary and has even been advised to
throw away telephone logs after a month (The New York Times,
November 7, 1993).
3 . An analogy to this is
as follows. Assume that there is a group of people at point A, and
they wish to deliver a light package to point B as soon as
possible. The speed at which the package can be delivered to point
B is solely a function of how long it would take the fastest person
to run from A to B. Having multiple people run from A to B will not
increase the speed at which the package can be
4 . For recent summaries of
court interpretations of the Fifth Amendment's bar on the
production of private papers see Jean F. Rydstrom, Supreme Courts
Views As To Application Of Fifth Amendment Privilege Against
Self-Incrimination To Compulsory Production Of Documents, 48 L.Ed.
2d 852 (1997); Anne Marie DeMarco & Elisa Scott, Note:
Confusion Among the Courts: Should the Contents Of Personal Papers
Be Privileged By The Fifth Amendment's Self-Incrimination Clause, 9
St. John's J.L. Comm 219 (1993); Suzanne Rosenthal Brackley,
Constitutional Law: Now It's Personal: Withdrawing the Fifth
Amendment's Content-Based Protection For All Private Papers In
United States v. Doe, 60 Brooklyn L. Rev. 553 (1994); and Sharon
Worthy-Bulla, An analysis of In re Grand Jury Subpoena Duces Tecum
(United States v. Doe): Does the Fifth Amendment Protect the
Contents of Private Papers?, 15 Pace L. Rev. 303 (1994).
5 . 116 U.S. 616
6 . Id. At
7 . 425 U.S. 391
8 . Id. at 409.
9 . Id. at 414.
10 . 465 U.S. 605, 618
11 . See Demarco and Scott,
supra note 4, for a description of current cases on the
12 . Senate Select
Committee On Ethics v. Senator Bob Packwood, 845 F. Supp. 17
13 . See Harold J. Krent,
Of Diaries and Data Banks: Use Restrictions Under the Fourth
Amendment 74 Tex L. Rev. 49 (1995) for a summary of Fourth
Amendment protections for private papers.
14 . Id.
15 . Id.
16 . 387 U.S.
17 . See Baird, Gertner and
Picker, Game Theory and the Law (1994) for a description of
18 . This is similar to the
argument for why prosecutors cannot mention to a jury that a
defendant has not testified. If prosecutors mention this to juries,
the jurors might infer that the defendant's silence means that the
defendant has something to hide. See Id.
19 . A.S. Tanenbaum,
Computer Networks , Prentice Hall, Third Edition,
20 . See infer note
21 . R.L. Rivest, A.
Shamir, and D.A. Wagner, 'Time-lock Puzzles and Timed-release
22 . M. Blaze, W. Diffie,
R.L. Rivest, B. Schneier, T. Shimomura, E. Thompson,and M. Wiener,
'Minimal Key Lengths for Symmetric Ciphers to Provide Adequate
Commercial Security', < http://theory.lcs.mit.edu/~rivest/bsa-final-report.ps >.