# An old _Discover_ article explaining RSA

years. It is a comic strip-type article by Larry Gonick article
explaining,
printed in the April 1992 issue of Discover magazine (some liberties
taken regarding pictures, etc.).

Box1:Prime Time
featuring SEYMOUR Cloak-and-Dagger Mathematician!
(sh!)
Box2:PRIME NUMBERS-numbers that can't be
broken into a product of smaller factors-
have always been one of the most amusing
and USELESS topics in mathematics.
Box3:Then why are Banks, Businesses, Mathematicians, and Government
SPY AGENCIES fighting over prime numbers?
(STOP RIGHT THERE!)
Box4:It has to do with CRYPTOGRAPHY-secret codes.
(The patriotic thing to do would be NOT to read one more word!)
Box5:In the computer age, cryptography is MATHEMATICAL: Inside the
computer, every MESSAGE is a string of ONES and
ZEROES: a number, in other words.
Box6:ENCRYPTING a message means scrambling this number,
using a reversible formula based on a secret number
or numbers called the KEY.
message-->key-->cyphertext
DECRYPTING the cyphertext is done by applying the
key in reverse.
Box7:It would seem that both the sender and receiver need to know-
and conceal-the key, but in the 1970's, WHITFIELD DIFFIE
and MARTIN HELLMAN showed a way to MAKE KEYS PUBLIC!
(Hippy-Diffie!)
Box8:Knowing how to SCRAMBLE, said Diffie, is not the same as
knowing how to UNSCRAMBLE. Consider the egg!!!
Box9:Suppose a code had TWO KEYS, a scrambler and an UNSCRAMBLER...
and suppose it was IMPOSSIBLE to compute one key from
the other-in the sense that no computer could do it in less
than the lifetime of the UNIVERSE???
(crank crank crank)
Box10:You'd have an UNBREAKABLE CODE!
(Wait... Almost got it...)
Box11:It works like this:
Everyone owns a unique pair of keys. One remains private.
But the other, public key is listed in a directory.
To send me a message, you look up my public key and use
it to scramble the message.
My private key is the only way to unlock the message.
Result:total secrecy and privacy!!
Box12:Diffie's idea soon became a reality, as three guys at M.I.T.
created
a public-key algorithm known as RSA, from their initials.
Box13:RSA's unbreakability depends on the "impossibility" of FACTORING
large numbers.
(15? that's 3 x 5! Easy!)
(3,447,981,101,346,271,113,552,476,003,201,
119,181,244,551,900,123,549,822,344,722,436,001? um..)
Box14:It's not hard to find two large PRIME NUMBERS P and Q. But if
I hand you their PRODUCT, PQ, your supercomputer will
never find P and Q again.
(SOB!)
Box15:Under RSA, each user gets a 160 digit number, N, which is the
product of two large primes, P and Q.
Box16:The number N is made public, while P and Q remain secret. A
simple formula completes the encryption, which can't be cracked
without FACTORING!
(ngh)
Box17:The National Security Agency didn't like this! The spy bureau wants
the ability to crack any code!
Box18:But spies aren't the only ones who need cryptography! Anyone who
transmits ELECTRONIC DATA wants to secure the information's
integrity.
(Why? What? This is an OPEN SOCIETY!)
Box19:Unbreakable public-key code would effectively
Protect money transfers from tampering
Shield sensitive business data from the competition
Immunize software against viruses
(Allow us to gossip securely by E-Mail!)
Box20:So-After years of resisting Public-Key systems, the government
in 1991 finally endorsed one as a new NATIONAL STANDARD.
(I WAS WRONG! EMBRACE ME!)
Box21:Unlike RSA, however, the government's DSA (Digital Signature
Algorithm) depends on a single, government-issue PRIME
NUMBER.
(Take a P! Not any P!)
Box22:Within months, mathematicians had shown how this could give
the government, and the government alone, the ability to
BREAK the code-and so the argument continues...
(Trust, Where is the trust??)