仅调用scanner一个库写RSA加密解密算法

RSA加密解密算法需要用到大数运算，Java中已经提供了BigInteger类用于处理大数运算，因此我们需要同时引入Scanner和BigInteger两个库。下面是一个简单的RSA加密解密代码示例：

import java.util.Scanner;
import java.math.BigInteger;

public class RSA {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        // 1. 选取两个不同的质数p和q
        System.out.print("Enter a prime number p: ");
        BigInteger p = sc.nextBigInteger();
        System.out.print("Enter another prime number q: ");
        BigInteger q = sc.nextBigInteger();

        // 2. 计算n = p * q 和φ(n) = (p - 1) * (q - 1)
        BigInteger n = p.multiply(q);
        BigInteger phi_n = p.subtract(BigInteger.ONE).multiply(q.subtract(BigInteger.ONE));

        // 3. 选择一个小于φ(n)的整数e，使得e与φ(n)互质
        System.out.print("Choose a number e that is relatively prime to " + phi_n + ": ");
        BigInteger e = sc.nextBigInteger();

        // 4. 计算e关于φ(n)的模反元素d
        BigInteger d = e.modInverse(phi_n);

        // 输出公钥和私钥
        System.out.println("Public key: (" + n + ", " + e + ")");
        System.out.println("Private key: (" + n + ", " + d + ")");

        // 加密
        System.out.print("Enter a message to encrypt: ");
        BigInteger message = sc.nextBigInteger();
        BigInteger encrypted = message.modPow(e, n);
        System.out.println("Encrypted message: " + encrypted);

        // 解密
        System.out.print("Enter a message to decrypt: ");
        BigInteger cipher = sc.nextBigInteger();
        BigInteger decrypted = cipher.modPow(d, n);
        System.out.println("Decrypted message: " + decrypted);
    }
}

注意，在输入p、q和e时，需要保证它们是质数或者与φ(n)互质的整数。此外，为了保证加密后的结果不超过n，输入的明文也需要是一个小于n的正整数。