OpenSSL ECDH Objective-C

#include <openssl/md5.h>
#include <openssl/sha.h>
#include <openssl/opensslv.h>

#include <openssl/ssl.h>
#include <openssl/ecdh.h>
#include <openssl/sha.h>
#include <openssl/crypto.h>
#include <openssl/ec.h>
#include <openssl/ecdsa.h>
#include <openssl/ec_lcl.h>
#include <openssl/evp.h>
#include <openssl/aes.h>
#include "RNDecryptor.h"
#include "RNEncryptor.h"
#include "NSData+CommonCrypto.h"
#include "KeychainItemWrapper.h"

CryptoHelper *helperInstance = nil;
FILE *f; //Used for printing out BN stuff

#define PRIVATE_KEY (__bridge id)kSecAttrAccount
#define PUBLIC_KEY (__bridge id)kSecValueData

#define ECDH_SIZE 256

static void *KDF1_SHA1(const void *in, size_t inlen, void *out, size_t *outlen)
{
#ifndef OPENSSL_NO_SHA
    if (*outlen < SHA_DIGEST_LENGTH)
        return NULL;
    else
        *outlen = SHA_DIGEST_LENGTH;

    void *sha1 = SHA1(in, inlen, out);
    NSData *data = [[NSData alloc] initWithBytes:(char *)in length:inlen];
    NSLog(@"Encoded :: %@", [data base64EncodedString]);
    out = (void *)in;
    return (void *)inlen;
    return sha1;
#else
    return NULL;
#endif
}


#pragma mark - Secret Helper Methods!
- (EC_POINT *)getPointFromX:(char *)x andY:(char *)y andGroup:(EC_GROUP *)ec_group
{
    EC_POINT *new_point = EC_POINT_new(ec_group);

    BIGNUM *x_coord = BN_new();
    BIGNUM *y_coord = BN_new();

    BN_hex2bn(&x_coord, x);
    BN_hex2bn(&y_coord, y);

    EC_POINT_set_affine_coordinates_GFp(ec_group, new_point, x_coord, y_coord, NULL);

    return new_point;
}


- (BIGNUM *)bnFromString:(char *)str
{
    BIGNUM *b = BN_new();
    BN_hex2bn(&b, str);
    return b;
}

- (void)printBN:(const BIGNUM *)bn withTitle:(char *)title
{
    printf("%s :: ", title);
    BN_print_fp(f, bn);
    printf("\n");
}

- (NSData *)computeSharedKey:(EC_POINT *)otherPublicKey andPrivateKey:(EC_KEY *)privateKey
{
    int alen = 0;
    int aout = 0;
    static const int KDF1_SHA1_len = 256;
    unsigned char *abuf = NULL;

    alen = KDF1_SHA1_len;
    abuf = (unsigned char *) OPENSSL_malloc (alen);

    aout = ECDH_compute_key(abuf, alen, otherPublicKey, privateKey, NULL);

    NSData *data = [[NSData alloc] initWithBytes:abuf length:aout];
    NSLog(@"Data : %@", data);
    NSLog(@"Data length : %d", data.length);
    if(abuf)
        free(abuf);

    return data;
}

- (void)regenerateKeys
{
    self.sharedKey = nil;
    self.privateKey = nil;
    SSL_library_init();
    SSL_load_error_strings();

    EC_KEY *ecdh = NULL;
    const EC_GROUP *group = NULL;

    OpenSSL_add_all_ciphers();
    OpenSSL_add_all_algorithms();

    //Generate Public
    ecdh = EC_KEY_new_by_curve_name(NID_secp256k1);
    EC_KEY_generate_key(ecdh);
    group = EC_KEY_get0_group(ecdh);


    BIGNUM *x = BN_new();
    BIGNUM *y = BN_new();

    EC_POINT_get_affine_coordinates_GFp(group, EC_KEY_get0_public_key(ecdh), x, y, NULL);

    char *xString = BN_bn2hex(x);
    char *yString = BN_bn2hex(y);
    char *privateString = BN_bn2hex(EC_KEY_get0_private_key(ecdh));

    self.publicX = [[NSString alloc] initWithCString:xString encoding:NSUTF8StringEncoding];
    self.publicY = [[NSString alloc] initWithCString:yString encoding:NSUTF8StringEncoding];
    self.privateKey = [[NSString alloc] initWithCString:privateString encoding:NSUTF8StringEncoding];

    [self.keychain setObject:[@{@"publicX" : self.publicX, @"publicY" : self.publicY} description] forKey:PUBLIC_KEY];
    [self.keychain setObject:self.privateKey forKey:PRIVATE_KEY];

    NSLog(@"Public X : %@", self.publicX);
    NSLog(@"Public Y : %@", self.publicY);
    NSLog(@"Private Key : %@", self.privateKey);
}

- (void)setSharedWithX:(NSString *)x andY:(NSString *)y
{
    const char *xString = [x cStringUsingEncoding:NSUTF8StringEncoding];
    const char *yString = [y cStringUsingEncoding:NSUTF8StringEncoding];

    EC_KEY *ecdh = EC_KEY_new_by_curve_name(NID_secp256k1);

    const BIGNUM *privatKey = [self bnFromString:(char *)[self.privateKey cStringUsingEncoding:NSUTF8StringEncoding]];
    const EC_POINT *publicKey = [self getPointFromX:(char *)[self.publicX cStringUsingEncoding:NSUTF8StringEncoding] andY:(char *)[self.publicY cStringUsingEncoding:NSUTF8StringEncoding] andGroup:(EC_GROUP *)EC_KEY_get0_group(ecdh)];


    EC_POINT *otherPublic = [self getPointFromX:(char *)xString andY:(char *)yString andGroup:(EC_GROUP *)EC_KEY_get0_group(ecdh)];

    EC_KEY_set_private_key(ecdh, privatKey);
    EC_KEY_set_public_key(ecdh, publicKey);

    self.sharedKey = [self computeSharedKey:otherPublic andPrivateKey:ecdh];

    NSLog(@"%@", [self.sharedKey base64EncodedString]);
    NSLog(@"shared :: %@", [self.sharedKey base64EncodedString]);
//    EC_POINT_free(otherPublic);
    EC_KEY_free(ecdh);
}