如果你想要要创建.PEM格式，您需要对 berData 方法的输出进行base64编码。您还需要添加页眉和页脚行。

If you want to create a .PEM format you need to base64 encode the output from the berData method. You also need to add the header and footer lines.

测试数据和代码，请参阅 bytesFromHexString $ c $的答案结尾C>：

Test data and code, see the end of the answer for bytesFromHexString:

NSString *modulusString =  @"c19bccae1e67743fab1c978f03122fb1a78ef05d565a2964728062ad0365e4751b8253df5fd13ab4ecb95c81ff17b91f969e4fb3d8274c30533338684278f6e5548027df775c055943a24a4117b0274c296c68b722c71670d4b21489a3da05d37ba06f2fb771b671a2c746bae4a049dc718fba19a75f1fb8ae1dd715b33d66a3";
NSString *exponentString = @"010001";

NSData *pubKeyModData = bytesFromHexString(modulusString);
NSData *pubKeyExpData = bytesFromHexString(exponentString);
NSArray *keyArray = @[pubKeyModData, pubKeyExpData];

//Given that you are using SCZ-BasicEncodingRules-iOS:
NSData *berData = [keyArray berData];
NSLog(@"berData:\n%@", berData);

NSString *berBase64 = [berData base64EncodedStringWithOptions:0];
NSString *preamble = @"-----BEGIN CERTIFICATE REQUEST-----";
NSString *postamble = @"-----END CERTIFICATE REQUEST-----";
NSString *pem = [NSString stringWithFormat:@"%@\n%@\n%@", preamble, berBase64, postamble];
NSLog(@"pem:\n%@", pem);

测试数据输出：

berData:
30818802 8180c19b ccae1e67 743fab1c 978f0312 2fb1a78e f05d565a 29647280 62ad0365 e4751b82 53df5fd1 3ab4ecb9 5c81ff17 b91f969e 4fb3d827 4c305333 38684278 f6e55480 27df775c 055943a2 4a4117b0 274c296c 68b722c7 1670d4b2 1489a3da 05d37ba0 6f2fb771 b671a2c7 46bae4a0 49dc718f ba19a75f 1fb8ae1d d715b33d 66a30203 010001

pem:
-----BEGIN CERTIFICATE REQUEST-----
  MIGIAoGAwZvMrh5ndD+rHJePAxIvsaeO8F1WWilkcoBirQNl5HUbglPfX9E6tOy5XIH/F7kflp5Ps9gnTDBTMzhoQnj25VSAJ993XAVZQ6JKQRewJ0wpbGi3IscWcNSyFImj2gXTe6BvL7dxtnGix0a65KBJ3HGPuhmnXx+4rh3XFbM9ZqMCAwEAAQ==
-----END CERTIFICATE REQUEST-----

将hex-ascii转换为数据：

Convert hex-ascii to data:

NSData* bytesFromHexString(NSString * aString) {
    NSString *theString = [[aString componentsSeparatedByCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]] componentsJoinedByString:nil];

    NSMutableData* data = [NSMutableData data];
    int idx;
    for (idx = 0; idx+2 <= theString.length; idx+=2) {
        NSRange range = NSMakeRange(idx, 2);
        NSString* hexStr = [theString substringWithRange:range];
        NSScanner* scanner = [NSScanner scannerWithString:hexStr];
        unsigned int intValue;
        if ([scanner scanHexInt:&intValue])
            [data appendBytes:&intValue length:1];
    }
    return data;
}