1. MSIT 543 Cryptography Concepts and Techniques How RSA Encryption Works
Dr Jeffrey A Robinson

2. How Encryption Works
From The Kahn Academy
Prior to the 1970’s encryption depended upoin symmetric keys, which can be safely exchanged.
But if keys need to be shared with MANY people, thousands of messages need to be transmitted to establish those many different keys.
This specific key exchange scenario is know as the Diffie-Hellman key exchange

3. RSA Encryption RSA encryption is based on Asymmetric keys
One to encrypt
And another to decrypt
The first is known as the public key..and anyone can encrypt
The second is the private key and can be used to decrypt the encoded message

4. RSA Encryption
The secret is the relation below (the enclosed link shows the origin and development of this function)
where K and n are very large primes

5. RSA Encryption Uses very large prime numbers p1 is a large prime
p2 is another large prime
n = p1*p2

6. RSA Encryption
Alice picks some numbers and does some math. She then publishes e and n (which together make up her public key).
(d in this case = 2011)

7. (Note: all digital objects are all numbers)
RSA Encryption
Encryption is performed by
me mod n = c
Where m is the message
And c is the encrypted result
(Note: all digital objects are all numbers)

8. RSA Encryption If the message, in our case, is 89, then c is 1394
(Remember, in real world cases, the numbers are many, many digits long)

9. RSA Encryption
Alice can then decrypt the message using her secret key “d”
By raising c to the power of d (which is m mod n)

10. revealing the original message
RSA Encryption
The result is decrypted
cd mod n = m or
mod 3127 = 89
revealing the original message

11. RSA Encryption When first discovered, it was immediately classified.
But it was rediscovered and published in 1977 by Ron Rivest, Adi Shamir, and Leonard Adleman at MIT
And is now known as RSA encryption
The letters RSA are the initials of their surnames, listed in the same order as on the paper