// for some reason we crash below on the Simulator but not on the actual device...
    NSURLCredential *credential = [NSURLCredential credentialWithIdentity:myIdentity
                                                             certificates:(NSArray *)myCerts
                                                              persistence:NSURLCredentialPersistenceForSession];

Here is the entire method:

- (void)connection:(NSURLConnection *)connection didReceiveAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge {
    NSString *certPath = [[NSBundle mainBundle] pathForResource:@"certificate" ofType:@"p12"];
    NSData *PKCS12Data = [NSData dataWithContentsOfFile:certPath];
    CFDataRef inPKCS12Data = (CFDataRef)PKCS12Data;
    SecCertificateRef myCert = SecCertificateCreateWithData(NULL, inPKCS12Data);
    SecIdentityRef myIdentity;
    SecTrustRef myTrust;
    OSStatus status = noErr;
    status = extractIdentityAndTrust(inPKCS12Data,
                                     &myIdentity,
                                     &myTrust);
    SecCertificateRef certArray[1] = { myCert };
    CFArrayRef myCerts = CFArrayCreate(NULL, (void *)certArray, 1, NULL);
    // for some reason we crash below on the Simulator but not on the actual device...
    NSURLCredential *credential = [NSURLCredential credentialWithIdentity:myIdentity
                                                             certificates:(NSArray *)myCerts
                                                              persistence:NSURLCredentialPersistenceForSession];
    CFRelease(myCerts);
    [challenge.sender useCredential:credential forAuthenticationChallenge:challenge];
}