Which equation is used to decrypt a message in RSA?

In the RSA encryption scheme, decryption involves the use of a specific mathematical equation that utilizes the ciphertext and the decryption key, typically denoted as ( d ), along with the modulus ( n ). The equation for decrypting a message is given by ( P = C^d \mod n ), where ( P ) is the plaintext message, ( C ) is the ciphertext, ( d ) is the private key exponent, and ( n ) is the product of two prime numbers used during the key generation process.

This equation works by raising the ciphertext to the power of ( d ) and then taking the modulo ( n ), which effectively reverses the encryption process conducted during the encryption stage, wherein the plaintext is raised to the power of the encryption key ( e ) and also taken modulo ( n ). The decryption successfully recovers the original plaintext ( P ) from the ciphertext ( C ).

Understanding this process is crucial because it illustrates the foundation of RSA's security, relying on the difficulty of factoring large prime products. The other choices do not accurately represent the decryption method used in RSA: options that mention ( C ) as a function of ( P ) or any incorrect operations