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#include <openssl/bn.h>
#include <stdio.h>

void printBN(const char *msg, BIGNUM *a) {
    char *number_str = BN_bn2dec(a);
    printf("%s%s\n", msg, number_str);
    OPENSSL_free(number_str);
}

int main() {
    BN_CTX *ctx = BN_CTX_new();

    // Initialize given values
    BIGNUM *p = BN_new();
    BIGNUM *q = BN_new();
    BIGNUM *n = BN_new();
    BIGNUM *phi_n = BN_new();
    BIGNUM *e = BN_new();
    BIGNUM *d = BN_new();
    BIGNUM *M = BN_new();
    BIGNUM *C = BN_new();

    // Assigning given values
    BN_set_word(p, 37);
    BN_set_word(q, 67);
    BN_set_word(e, 169);
    BN_set_word(M, 1234);

    // Calculate n = p * q
    BN_mul(n, p, q, ctx);

    // Calculate phi(n) = (p - 1) * (q - 1)
    BIGNUM *p_minus_1 = BN_new();
    BIGNUM *q_minus_1 = BN_new();
    BN_sub(p_minus_1, p, BN_value_one());
    BN_sub(q_minus_1, q, BN_value_one());
    BN_mul(phi_n, p_minus_1, q_minus_1, ctx);

    // Calculate d, the modular inverse of e modulo phi(n)
    BN_mod_inverse(d, e, phi_n, ctx);

    // Encrypt: C = M^e mod n
    BN_mod_exp(C, M, e, n, ctx);

    // Output the results
    printBN("Modulus n: ", n);
    printBN("Totient phi(n): ", phi_n);
    printBN("Private key d: ", d);
    printBN("Ciphertext C: ", C);

    // Cleanup
    BN_free(p);
    BN_free(q);
    BN_free(n);
    BN_free(phi_n);
    BN_free(e);
    BN_free(d);
    BN_free(M);
    BN_free(C);
    BN_CTX_free(ctx);

    return 0;
}
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