RSA encryption and decryption algorithms

1
RSA encryption and decryption algorithms

• Get 1st Prime Number called p
• Get 2nd Prime Number called q
• Set n p q
• Set m (p-1) (q-1)
• Find the Encryption key e
• (the key that has no common factor
  between any non-zero integer and m)
• Find the Decryption Key d
• (the key is that (x m 1) can be
  divided evenly by e, where x is an positive
  integer
• A. How to use the encryption key e to encrypt
  data W?

• Question 1. Using the RSA encryption algorithm,
• let p 3 and q 7.
• A. What is the encrypted code for 3? ______
• B. What is the decrypted code for 2? ______
• Solution
• 1. p 3
• 2. q 7
• 3. n 21
• 4. m (3-1) (7-1) 12
• 5. Find the Encryption key e
• Assume that e is 1. Any common factor between
  m12 and e1? Yes.
• Assume that e is 2. Any common factor between
  m12 and e2? Yes.
• Assume that e is 3. Any common factor
  between m12 and e3? Yes.
• Assume that e is 4. Any common factor between
  m12 and e4? Yes.
• Assume that e is 5. Any common factor between
  m12 and e5? No.
• You found it. e is 5.
• 6. Find the Decryption key d

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Practice Quiz

• Question 2. Using the RSA encryption algorithm,
  let p 2 and q 7.
• What is the encrypted code for 3? _____5_____
• What is the decrypted code for 2? _____4_____
• Steps to solve the problem
• 1. p 2
• 2. q 7
• 3. n 14
• 4. m (2-1) (7-1) 6
• 5. Find the Encryption key
• Assume that e is 1. Any common factor between
  m6 and e1? Yes.
• Assume that e is 2. Any common factor between
  m6 and e2? Yes.
• Assume that e is 3. Any common factor
  between m6 and e3? Yes.
• Assume that e is 4. Any common factor between
  m6 and e4? Yes.
• Assume that e is 5. Any common factor between
  m6 and e5? No.
• You found it. e is 5.
• 6. Find the Decryption key
• Can (1 m 1) divided by e5? No
• Can (2 m 1) divided by e5? No.