[Cryptography] Questions about crypto that lay people want to understand

Henry Baker hbaker1 at pipeline.com
Sat Dec 19 14:22:07 EST 2015

In gathering material for a crypto talk to
laypersons, I've been trying to collect a
number of questions that such laypersons
would like to know the answers to.

This talk is about the fundamental ideas
of crypto, and not addressing details of
HTTPS, so it's not a grown-up version of
a "crypto party".

I have my own ideas for answers to some
of these questions, but I'd be curious as
to what others on this list think.

BTW, some of these questions will stump
the best experts, but people will ask

[These questions are in no particular

* Ordinary citizens lived thousands of
years in sophisticated societies and
never needed clever crypto.  I don't
recall any crypto in the Bible, and the
only discussion of crypto in novels
seems to occur in the context of war
or high politics -- e.g., Queen Mary
of Scots.

Why now?  What is it about modern
society that seems to require crypto
for us ordinary citizens?

* We just had a crypto war in the
1990's, and everyone thought the
problem was solved.  Why are we
having another crypto war 20 years
later?  Is this a generational
phenomenon?  Or is this a periodic
cicada phenomenon?  Will there be
a quantum crypto war in 2035 ?

* Why the intimate connection
between crypto and randomness?
This connection seems very odd,
since encrypted text must be
capable of being *decrypted* back
into plaintext, and therefore
even seemingly random ciphertext
must have significant structure.

* SW/HW engineers and crypto
folks both use the word "code" to
indicate that some additional
structure has been added to
ordinary ASCII text in order to
achieve certain goals -- e.g.,
error detection, error correction,
confidentiality, integrity.  Are
these uses of "code" indicative
of any deeper relationship between
the different fields?

* What is the relationship
between the "key" in my pocket
and a crypto "key" ?

* Crypto techniques seem to
involve *cycles* -- e.g. modular
arithmetic, etc.  Why do cyclic
and circular things keep showing
up in crypto ?

* (For the physicist/EE.) What
is the relationship between
"information" in "information
theory" and "quantum theory" ?
Why the complete disconnect
between the quantum world and
information theory/crypto ?

* Why are some things hard to
compute?  Can't we just get
the cleverest people from MIT,
Stanford, (insert your favorite
here) to work on this?  If we
can build an H-bomb, make it
to the Moon and back, and
translate languages (thank
you, Google!), what's the
matter with you guys?

* If HTTPS is good enough for
my bank account, how come I
can't use it to vote?  Why
do I have to vote in person?

* Speaking of banking, will
digital currency replace
paper money?

* What is "strong" crypto?
Some products say that they
use "government quality"
crypto.  Will I be twice as
safe with 2048-bit keys as
with 1024-bit keys?

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