Encryption between C and C#

#include  #include    static char encoding_table[] = {'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H',                                 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',                                 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',                                 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',                                 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',                                 'o', 'p', 'q', 'r', 's', 't', 'u', 'v',                                 'w', 'x', 'y', 'z', '0', '1', '2', '3',                                 '4', '5', '6', '7', '8', '9', '+', '/'}; static char *decoding_table = NULL; static int mod_table[] = {0, 2, 1};   char *base64_encode(const unsigned char *data,                     size_t input_length,                     size_t *output_length) {      *output_length = 4 * ((input_length + 2) / 3);      char *encoded_data = malloc(*output_length);     if (encoded_data == NULL) return NULL;      for (int i = 0, j = 0; i < input_length;) {          uint32_t octet_a = i < input_length ? (unsigned char)data[i++] : 0;         uint32_t octet_b = i < input_length ? (unsigned char)data[i++] : 0;         uint32_t octet_c = i < input_length ? (unsigned char)data[i++] : 0;          uint32_t triple = (octet_a << 0x10) + (octet_b << 0x08) + octet_c;          encoded_data[j++] = encoding_table[(triple >> 3 * 6) & 0x3F];         encoded_data[j++] = encoding_table[(triple >> 2 * 6) & 0x3F];         encoded_data[j++] = encoding_table[(triple >> 1 * 6) & 0x3F];         encoded_data[j++] = encoding_table[(triple >> 0 * 6) & 0x3F];     }      for (int i = 0; i < mod_table[input_length % 3]; i++)         encoded_data[*output_length - 1 - i] = '=';      return encoded_data; }

byte[] data = Convert.FromBase64String(encodedString); string decodedString = Encoding.UTF8.GetString(data);