Cryptography/Bit of Memory

Caesar Cipher

Symmetric encryption technique that shifts the alphabet by a specified # and rewrites the original message with the new alphabet

One-Time Pad

Symmetric Encryption technique that has a different shift for each letter of the message. Only secure for one-time use

Problems of Symmetric Encryption

Requires sharing the key somehow, can be vulnerable to frequency analysis for shifts, only meant for one pair to share messages

Public Key Cryptography

Asymmetric Encryption scheme where messages are encoded by the sender using the receiver’s public key and decoded by the receiver using their private key.

RSA Public Key

(n, e)

RSA n

The product of two unique prime numbers, p and q

RSA e

A number relatively prime to (p-1)(q-1) and <n, (11 is always a safe e value)

RSA d (private key)

Found by taking (1/e)mod (p-1)(q-1)

RSA Encryption

m ^e mod n

RSA Decryption

<encrypted message>^d mod n

PFP/Previous Frame Pointer

Points to previous frame on the stack to return to

Return Address

Points to machine code to return to

Integer Memory size

4 bytes

Char Memory Size

1 byte

Double Memory Size

8 bytes

Pointer Memory Size

8 bytes

Parameter’s Positions on the Stack Frame

Added before the RA and PFP for a new stack frame

Current Frame Pointer

Points at currently active frame, is switched to the PFP once the current frame is done

Direction data writes

Towards high memory addresses