A shift cipher (Caesar cipher) is a basic method of symmetric encryption used to protect digital data.
Using modular arithmetic where the letters A to Z are mapped to the integers 0 to 25, write down mathematical formulas to represent:
the encryption of a plaintext letter p p\,p to a ciphertext letter c c\,c using a shift key kkk,
the decryption of the ciphertext letter c c\,c back to the plaintext letter ppp.
Practise Edexcel GCSE Computer Science Cybersecurity with exam-style questions for GCSE Computer Science. 41 questions covering Malware threats and cyberattack methods and Protecting digital systems and data, matched to the Edexcel GCSE Computer Science (1CP2) specification and written in Paper 1 and Paper 2 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.