我正在为ios和Android开发应用程序。我对加密任务比较陌生，在过去的3天里，我不停地撞墙，因为我无法运行RSA加密。
两个客户端都从java服务器接收公钥。在android我有（显然，因为它几乎与服务器端的代码相同）没有麻烦，但ios部分似乎根本不兼容。我想用公钥加密一小段数据（aes密钥），这就是我在Java中的做法：
try {
String publickey = "MCwwDQYJKoZIhvcNAQEBBQADGwAwGAIRAK+dBpbOKw+1VKMWoFxjU6UCAwEAAQ==";
byte[] bArr = Crypto.base64Decode(publicKey, false);
KeyFactory keyFactory = KeyFactory.getInstance("RSA", "BC");
EncodedKeySpec publicKeySpec = new X509EncodedKeySpec(publicKey);
PublicKey publicKey = keyFactory.generatePublic(publicKeySpec);
Cipher cipher = Cipher.getInstance("RSA/NONE/PKCS1Padding", "BC");
cipher.init(1,publicKey);
int cipherBlockSize = cipher.getBlockSize();
ByteArrayOutputStream bArrOut = new ByteArrayOutputStream();
bArrOut.flush();
int pos = 0;
Log.i("ContentBufferLength", contentBuffer.length+"");
while (true) {
if (cipherBlockSize > contentBuffer.length - pos) {
cipherBlockSize = contentBuffer.length - pos;
}
Log.i("CipherBlockSize", cipherBlockSize+"");
byte[] tmp = cipher.doFinal(contentBuffer, pos, cipherBlockSize);
bArrOut.write(tmp);
pos += cipherBlockSize;
if (contentBuffer.length <= pos) {
break;
}
}
bArrOut.flush();
encryptedBuffer = bArrOut.toByteArray();
bArrOut.close();
} catch (Exception ex) {
throw ex;
}
// Log.i("Encrypted Buffer Length", encryptedBuffer.length+"");
return encryptedBuffer;
这是我的（不正常工作）ios代码，借鉴于此：
http://blog.wingsofhermes.org/?p=75和苹果加密练习。
-(NSString* )encryptWithPublicKey:(NSString*)key input:(NSString*) input {
const size_t BUFFER_SIZE = 16;
const size_t CIPHER_BUFFER_SIZE = 16;
//const uint32_t PADDING = kSecPaddingNone;
const uint32_t PADDING = kSecPaddingPKCS1;
static const UInt8 publicKeyIdentifier[] = "de.irgendwas.app";
NSData *publicTag;
publicTag = [[NSData alloc] initWithBytes:publicKeyIdentifier length:sizeof(publicKeyIdentifier)];
NSMutableDictionary *publicKey2 = [[NSMutableDictionary alloc] init];
[publicKey2 setObject:kSecClassKey forKey:kSecClass];
[publicKey2 setObject:kSecAttrKeyTypeRSA forKey:kSecAttrKeyType];
[publicKey2 setObject:publicTag forKey:kSecAttrApplicationTag];
SecItemDelete((CFDictionaryRef)publicKey2);
NSData *strippedPublicKeyData = [NSData dataFromBase64String:key];
unsigned char * bytes = (unsigned char *)[strippedPublicKeyData bytes];
size_t bytesLen = [strippedPublicKeyData length];
size_t i = 0;
if (bytes[i++] != 0x30)
[Exception raise:FAILURE function:__PRETTY_FUNCTION__ line:__LINE__ description:@"Could not set public key."];
/* Skip size bytes */
if (bytes[i] > 0x80)
i += bytes[i] - 0x80 + 1;
else
i++;
if (i >= bytesLen)
[Exception raise:FAILURE function:__PRETTY_FUNCTION__ line:__LINE__ description:@"Could not set public key."];
if (bytes[i] != 0x30)
[Exception raise:FAILURE function:__PRETTY_FUNCTION__ line:__LINE__ description:@"Could not set public key."];
/* Skip OID */
i += 15;
if (i >= bytesLen - 2)
[Exception raise:FAILURE function:__PRETTY_FUNCTION__ line:__LINE__ description:@"Could not set public key."];
if (bytes[i++] != 0x03)
[Exception raise:FAILURE function:__PRETTY_FUNCTION__ line:__LINE__ description:@"Could not set public key."];
/* Skip length and null */
if (bytes[i] > 0x80)
i += bytes[i] - 0x80 + 1;
else
i++;
if (i >= bytesLen)
[Exception raise:FAILURE function:__PRETTY_FUNCTION__ line:__LINE__ description:@"Could not set public key."];
if (bytes[i++] != 0x00)
[Exception raise:FAILURE function:__PRETTY_FUNCTION__ line:__LINE__ description:@"Could not set public key."];
if (i >= bytesLen)
[Exception raise:FAILURE function:__PRETTY_FUNCTION__ line:__LINE__ description:@"Could not set public key."];
strippedPublicKeyData = [NSData dataWithBytes:&bytes[i] length:bytesLen - i];
DLog(@"X.509 Formatted Public Key bytes:\n%@",[strippedPublicKeyData description]);
if (strippedPublicKeyData == nil)
[Exception raise:FAILURE function:__PRETTY_FUNCTION__ line:__LINE__ description:@"Could not set public key."];
CFTypeRef persistKey = nil;
[publicKey2 setObject:strippedPublicKeyData forKey:kSecValueData];
[publicKey2 setObject: (kSecAttrKeyClassPublic) forKey:kSecAttrKeyClass];
[publicKey2 setObject:[NSNumber numberWithBool:YES] forKey:kSecReturnPersistentRef];
OSStatus secStatus = SecItemAdd((CFDictionaryRef)publicKey2, &persistKey);
if (persistKey != nil) CFRelease(persistKey);
if ((secStatus != noErr) && (secStatus != errSecDuplicateItem))
[Exception raise:FAILURE function:__PRETTY_FUNCTION__ line:__LINE__ description:@"Could not set public key."];
SecKeyRef keyRef = nil;
[publicKey2 removeObjectForKey:kSecValueData];
[publicKey2 removeObjectForKey:kSecReturnPersistentRef];
[publicKey2 setObject:[NSNumber numberWithBool:YES] forKey:kSecReturnRef];
[publicKey2 setObject: kSecAttrKeyTypeRSA forKey:kSecAttrKeyType];
SecItemCopyMatching((CFDictionaryRef)publicKey2,(CFTypeRef *)&keyRef);
if (!keyRef)
[Exception raise:FAILURE function:__PRETTY_FUNCTION__ line:__LINE__ description:@"Could not set public key."];
uint8_t *plainBuffer;
uint8_t *cipherBuffer;
uint8_t *decryptedBuffer;
const char inputString[] = "1234";
int len = strlen(inputString);
// TODO: this is a hack since i know inputString length will be less than BUFFER_SIZE
if (len > BUFFER_SIZE) len = BUFFER_SIZE-1;
plainBuffer = (uint8_t *)calloc(BUFFER_SIZE, sizeof(uint8_t));
cipherBuffer = (uint8_t *)calloc(CIPHER_BUFFER_SIZE, sizeof(uint8_t));
decryptedBuffer = (uint8_t *)calloc(BUFFER_SIZE, sizeof(uint8_t));
strncpy( (char *)plainBuffer, inputString, len);
size_t plainBufferSize = strlen((char *)plainBuffer);
size_t cipherBufferSize = CIPHER_BUFFER_SIZE;
NSLog(@"SecKeyGetBlockSize() public = %lu", SecKeyGetBlockSize(keyRef));
// Error handling
// Encrypt using the public.
OSStatus status = noErr;
status = SecKeyEncrypt(keyRef,
PADDING,
plainBuffer,
plainBufferSize,
&cipherBuffer[0],
&cipherBufferSize
);
NSLog(@"encryption result code: %ld (size: %lu)", status, cipherBufferSize);
return [[[NSString stringWithFormat:@"%s",cipherBuffer] dataUsingEncoding:NSUTF8StringEncoding] base64EncodedString];
}
出于测试目的和简单性，我试图仅加密长度为4个字节的输入。这应该小到足以适合一个街区。公钥导入和加密过程似乎有效，但与android方法相比，我总是会收到更长的输出。
我到目前为止遇到的唯一区别是事实，SecKeyGetBlockSize returns 16和java cipher.blocksize返回5.我认为其他11个字节是为pkcs1填充保留的，但是如何强制执行相同的行为ios/objc？
答案 0 :(得分：1)
尝试将密文分成多个部分，以便每个部分包含16个字符长并分别解码它们。我也遇到了同样的问题，但是在PHP中很长一段时间以及上面的技巧对我有效。
这可能有助于您摆脱问题。
答案 1 :(得分：1)
解码Base64密钥给出：
MCwwDQYJKoZIhvcNAQEBBQADGwAwGAIRAK+dBpbOKw+1VKMWoFxjU6UCAwEAAQ==
-> 302c300d06092a864886f70d0101010500031b003018021100af9d0696ce2b0fb554a316a05c6353a50203010001
将此解释为DER编码的ASN.1，我们发现：
30(2c) //SEQUENCE
30(0d) //SEQUENCE
06(09): 2a 86 48 86 f7 0d 01 01 01 //OID 1.2.840.113548.1.1.1 (RSA Encryption)
05(00): //NULL
03(1b): [00] 30 18 02 11 00 af 9d 06 96 ce 2b 0f b5 54 a3 16 a0 5c 63 53 a5 02 03 01 00 01 //BITSTRING
BITSTRING似乎也包含DER编码的ASN.1：
30(18) //SEQUENCE
02(11): 00 af 9d 06 96 ce 2b 0f b5 54 a3 16 a0 5c 63 53 a5 02 03 01 00 01 //INTEGER
= 0xaf9d0696ce2b0fb554a316a05c6353a50203010001
通过IOS代码，您可以看到它正在解析DER编码的ASN.1。它正确识别前两个SEQUENCE标记，并跳过OID字段，甚至不验证它是否为OID。然后出现问题：IOS代码需要下一个标记 BITSTRING（0x03）---但在我们的数据中，我们有一个额外的NULL（0x05）字段来表示公共指数是隐式的。 IOS代码在遇到0x05标记时引发异常。如果没有NULL，我们会看到IOS代码已经成功提取了BITSTRING的内容。
所以：NULL是一个可选字段，IOS代码不允许它，或者IOS代码期望不同的ASN.1结构。例如，看起来BITSTRING也是DER编码的ASN.1 INTEGER（可能是RSA模数）。然而IOS代码没有尝试解析它。可能是IOS SecKeyEncrypt例程期望模数的这种格式，或者可能是调用者应该提取模数的原始字节。
所以还需要一些实验。但是，如果此代码要解析所提供的数据对象，则必须使用以下附加条件：
/* Skip OID */
i += 15;
if (i >= bytesLen - 2)
[Exception raise:FAILURE function:__PRETTY_FUNCTION__ line:__LINE__ description:@"Could not set public key."];
if (bytes[i] == 0x05) /* This should handle the spurious ASN.1 NULL field */
i += 2;
if (bytes[i++] != 0x03)
答案 2 :(得分：0)
在Android或Java中，生成的密钥采用标准ASN.1格式，该格式在外部环境（客户端，服务器端）运行良好，但在iOS中，生成的密钥（公共，私有）采用原始格式，因此您必须将其转换为正确的ASN.1格式以使其可行。