Rivest Shamir Aldeman Block Cipher

The RSA algorithm is a block cipher in which the plaintext and ciphertext are integers between $0$ and $n-1$ for some $n$.

• Typically $n$ is $1024$ bits ($309$ decimal digits)

The security of the algorithm comes from the difficulty of factoring large numbers. Keys are functions of pairs of large, $\ge 100$ digit, prime numbers.