blocks|key|31143|text|获得BCRYPT_SECRET_HANDLE后，您可以使用BCryptDeriveKey来获得实际的对称加密密钥。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|31144|entityMap^0|2|K|T|F|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|M|8|@]|D|@]|E|$]]]|G|$]]

Once you got your <code>BCRYPT_SECRET_HANDLE</code>, you use <code>BCryptDeriveKey</code> to obtain the actual symmetric encryption key.

blocks|key|31512|text|在调用BCryptSecretAgreement之后，您需要使用BCryptDeriveKey函数来检索共享密钥。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|31513|这可以按如下方式完成：|31514|//+generates+an+ECDH+shared+secret+from+a+public+key+and+a+private+key
int+get_ECDH_key(BCRYPT_KEY_HANDLE+pubkey,+BCRYPT_KEY_HANDLE+privkey,+unsigned+char+**key,
+++++++++++++++++unsigned+int+*keylen)
{
++++SECURITY_STATUS+sstatus;
++++BCRYPT_SECRET_HANDLE+secret;
++++int+_len;

++++//+creates+the+shared+secret,+stored+in+a+BCRYPT_SECRET_HANDLE+
++++sstatus+=+BCryptSecretAgreement(privkey,+pubkey,+&secret,+0);
++++if+(!BCRYPT_SUCCESS(sstatus))+{
++++++++printf("BCryptSecretAgreement+failed+with+status+%25d",+sstatus);
++++++++return+0;
++++}

++++//+find+out+how+much+space+is+needed+before+retrieving+the+shared+secret
++++sstatus+=+BCryptDeriveKey(secret,+BCRYPT_KDF_HASH,+NULL,+NULL,+0,+&_len,+0);
++++if+(!BCRYPT_SUCCESS(sstatus))+{
++++++++printf("BCryptDeriveKey+failed+with+status+%25d",+sstatus);
++++++++return+0;
++++}

++++//+allocate+space+for+the+shared+secret
++++*key+=+malloc(_len);
++++if+(*key+==+NULL)+{
++++++++perror("malloc+failed");
++++++++exit(1);
++++}

++++//+retrieve+the+shared+secret
++++sstatus+=+BCryptDeriveKey(secret,+BCRYPT_KDF_HASH,+NULL,+*key,+_len,
++++++++++++++++++++++++++++++keylen,+0+);
++++if+(!BCRYPT_SUCCESS(sstatus))+{
++++++++printf("BCryptDeriveKey+failed+with+status+%25d",+sstatus);
++++++++return+0;
++++}
++++return+1;
}|code-block|syntax|javascript|31515|对于第二个参数，常量BCRYPT_KDF_HASH表示使用散列作为密钥派生函数。可以在第三个参数中指定要使用的散列。在本例中，第三个参数为NULL，因此默认情况下使用SHA1。|31516|此外，第四个参数可以是NULL，它是指向接收密钥的缓冲区的指针。如果是，则不复制密钥，但是将复制的字节数写入第六个参数给定的地址。这允许我们分配适当的空间量，然后再次调用函数，这次传入分配的缓冲区的地址。|31517|entityMap|0|LINK|mutability|MUTABLE|url|https://msdn.microsoft.com/en-us/library/windows/desktop/aa375393(v=vs.85).aspx^0|3|L|W|F|W|F|0|0|0|0|A|F|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@$9|Z|A|10|B|C]|$9|11|A|12|B|C]]|D|@$9|13|A|14|1|15]]|E|$]]|$1|F|3|G|5|6|7|16|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|17|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|18|8|@$9|19|A|1A|B|C]]|D|@]|E|$]]|$1|O|3|P|5|6|7|1B|8|@]|D|@]|E|$]]|$1|Q|3|-4|5|6|7|1C|8|@]|D|@]|E|$]]]|R|$S|$5|T|U|V|E|$W|X]]]]

After calling <code>BCryptSecretAgreement</code>, You need to use the <a href="https://msdn.microsoft.com/en-us/library/windows/desktop/aa375393(v=vs.85).aspx" rel="nofollow noreferrer"><code>BCryptDeriveKey</code></a> function to retrieve the shared secret.

This can be done as follows:

<pre><code>// generates an ECDH shared secret from a public key and a private key
int get_ECDH_key(BCRYPT_KEY_HANDLE pubkey, BCRYPT_KEY_HANDLE privkey, unsigned char **key,
 unsigned int *keylen)
{
 SECURITY_STATUS sstatus;
 BCRYPT_SECRET_HANDLE secret;
 int _len;

 // creates the shared secret, stored in a BCRYPT_SECRET_HANDLE 
 sstatus = BCryptSecretAgreement(privkey, pubkey, &amp;secret, 0);
 if (!BCRYPT_SUCCESS(sstatus)) {
 printf("BCryptSecretAgreement failed with status %d", sstatus);
 return 0;
 }

 // find out how much space is needed before retrieving the shared secret
 sstatus = BCryptDeriveKey(secret, BCRYPT_KDF_HASH, NULL, NULL, 0, &amp;_len, 0);
 if (!BCRYPT_SUCCESS(sstatus)) {
 printf("BCryptDeriveKey failed with status %d", sstatus);
 return 0;
 }

 // allocate space for the shared secret
 *key = malloc(_len);
 if (*key == NULL) {
 perror("malloc failed");
 exit(1);
 }

 // retrieve the shared secret
 sstatus = BCryptDeriveKey(secret, BCRYPT_KDF_HASH, NULL, *key, _len,
 keylen, 0 );
 if (!BCRYPT_SUCCESS(sstatus)) {
 printf("BCryptDeriveKey failed with status %d", sstatus);
 return 0;
 }
 return 1;
}
</code></pre>

For the second parameter, the constant <code>BCRYPT_KDF_HASH</code> says to use a hash as the key derivation function. The hash to use can be specified in the third parameter. In this example, the third parameter is NULL, so it uses SHA1 by default.

Also, the fourth parameter, which is a pointer to the buffer to receive the key, can be NULL. If so, the key is not copied however the number of bytes that would be copied are written to the address given by the sixth parameter. This allows us to allocate the proper amount of space then call the function again, this time passing in the address of the allocated buffer.

blocks|key|2494587|text|从Windows10开始，你可以用BCRYPT_KDF_RAW_SECRET调用BCryptDeriveKey()。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2494588|所得到的密钥数据是原始的秘密。|2494589|注1:+bcrypt.h表示此格式适用于"WINBLUE"，如果我理解正确的话，它将是Windows8.1，但我收到了在Windows8.1和Windows+Server2012+R2上使用此KDF类型的STATUS_NOT_SUPPORTED。然而，这在Windows+10上是有效的。)|2494590|Note2:我发现使用这种KDF类型返回的数据是小端的(+BCrypt中的其他所有内容都是大端的)。因此，要在其他高端世界中使用该值，您需要对数据进行字节翻转。|2494591|entityMap^0|H|L|14|H|0|0|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@$9|O|A|P|B|C]|$9|Q|A|R|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|S|8|@]|D|@]|E|$]]|$1|H|3|I|5|6|7|T|8|@]|D|@]|E|$]]|$1|J|3|K|5|6|7|U|8|@]|D|@]|E|$]]|$1|L|3|-4|5|6|7|V|8|@]|D|@]|E|$]]]|M|$]]

Starting with Windows 10, you can call <code>BCryptDeriveKey()</code> with <code>BCRYPT_KDF_RAW_SECRET</code>. 

The resulting key data is the raw secret.

Note 1: bcrypt.h indicates that this format works for "WINBLUE", which would be Windows 8.1, if I understand correctly, but I received STATUS_NOT_SUPPORTED for the use of this KDF type on both Windows 8.1 and Windows Server 2012 R2. This works, however, on Windows 10.)

Note2: I found the data returned using this KDF type to be little-endian (where everything else in BCrypt is big-endian). So, to use the value in an otherwise big-endian world, you need to byte-flip the data.

blocks|key|31166|text|我需要执行以下操作，以下是执行关键项目的代码的摘录，您需要在此段之前导入私钥和公钥|type|unstyled|depth|inlineStyleRanges|entityRanges|data|31167|DWORD+bCryptStatus;
BCRYPT_SECRET_HANDLE+secretHandle+=+NULL;
BCRYPT_KEY_HANDLE+privateKeyHandle=+NULL;
BCRYPT_KEY_HANDLE+importedPublicKey+=+NULL;
BYTE+*agreedSecret+=+NULL;
DWORD+agreedSecretLength+=+0;

//Import+your+keys+here

//Generate+the+secret+from+the+imported+keys
bCryptStatus=+BCryptSecretAgreement(privateKeyHandle,+importedPublicKey,+&secretHandle,+0);

//Now+get+the+raw+value+of+the+secret+agreement+and+copy+it+into+an+array
bCryptStatus=+BCryptDeriveKey(
++++secretHandle,++++++++++//+Secret+agreement+handle
++++BCRYPT_KDF_RAW_SECRET,+//+Key+derivation+function+(null+terminated+unicode+string)
++++NULL,++++++++++++++++++//+KDF+parameters
++++NULL,++++++++++++++++++//+Buffer+that+recieves+the+derived+key+
++++0,+++++++++++++++++++++//+Length+of+the+buffer
++++&agreedSecretLength,+++//+Number+of+bytes+copied+to+the+buffer
++++0);++++++++++++++++++++//+Flags

++++agreedSecret+=+(PBYTE)MALLOC(agreedSecretLength);

if+(NULL+!=+agreedSecret)
{
++++_nCryptError+=+BCryptDeriveKey(
++++secretHandle,++++++++++//+Secret+agreement+handle
++++BCRYPT_KDF_RAW_SECRET,+//+Key+derivation+function+(null+terminated+unicode+string)
++++NULL,++++++++++++++++++//+KDF+parameters
++++agreedSecret,++++++++++//+Buffer+that+recieves+the+derived+key+
++++agreedSecretLength,++++//+Length+of+the+buffer
++++&agreedSecretLength,+++//+Number+of+bytes+copied+to+the+buffer
++++0);++++++++++++++++++++//+Flags
}

//Free+all+the+objects+and+the+array+when+you+are+done,+otherwise+you+will+get+memory+leaks
if+(NULL+!=+importedPublicKey)
{
++++BCryptDestroyKey(importedPublicKey);
}

if+(NULL+!=+privateKeyHandle)
{
++++BCryptDestroyKey(privateKeyHandle);
}

if+(NULL+!=+secretHandle)
{
++++BCryptDestroySecret(secretHandle);
}

if+(NULL+!=+agreedSecret)
{
++++FREE(agreedSecret);
}|code-block|syntax|javascript|31168|顺便说一句，如果你使用NCrypt，这也会起作用(NCryptDeriveKey)，我在我的生产代码中验证了它。如前所述，数组将被颠倒，您将需要颠倒字节数组来获取秘密。|31169|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

I needed to do the following, and here is an excerpt from my code which does the critical items, you will need to import the private and public keys before this segment

<pre><code>DWORD bCryptStatus;
BCRYPT_SECRET_HANDLE secretHandle = NULL;
BCRYPT_KEY_HANDLE privateKeyHandle= NULL;
BCRYPT_KEY_HANDLE importedPublicKey = NULL;
BYTE *agreedSecret = NULL;
DWORD agreedSecretLength = 0;

//Import your keys here

//Generate the secret from the imported keys
bCryptStatus= BCryptSecretAgreement(privateKeyHandle, importedPublicKey, &amp;secretHandle, 0);

//Now get the raw value of the secret agreement and copy it into an array
bCryptStatus= BCryptDeriveKey(
 secretHandle, // Secret agreement handle
 BCRYPT_KDF_RAW_SECRET, // Key derivation function (null terminated unicode string)
 NULL, // KDF parameters
 NULL, // Buffer that recieves the derived key 
 0, // Length of the buffer
 &amp;agreedSecretLength, // Number of bytes copied to the buffer
 0); // Flags

 agreedSecret = (PBYTE)MALLOC(agreedSecretLength);

if (NULL != agreedSecret)
{
 _nCryptError = BCryptDeriveKey(
 secretHandle, // Secret agreement handle
 BCRYPT_KDF_RAW_SECRET, // Key derivation function (null terminated unicode string)
 NULL, // KDF parameters
 agreedSecret, // Buffer that recieves the derived key 
 agreedSecretLength, // Length of the buffer
 &amp;agreedSecretLength, // Number of bytes copied to the buffer
 0); // Flags
}

//Free all the objects and the array when you are done, otherwise you will get memory leaks
if (NULL != importedPublicKey)
{
 BCryptDestroyKey(importedPublicKey);
}

if (NULL != privateKeyHandle)
{
 BCryptDestroyKey(privateKeyHandle);
}

if (NULL != secretHandle)
{
 BCryptDestroySecret(secretHandle);
}

if (NULL != agreedSecret)
{
 FREE(agreedSecret);
}

</code></pre>

As a side note, if you use NCrypt, this will work also (NCryptDeriveKey), I verified it on my production code.
As it was stated earlier, the array will be reversed, and you will need to reverse the array of bytes to get the secret.

I'm implementing ECDHE using crypto next generation APIs (CNG). I generate public and private keys successfully. For pre-shared key, I use <a href="https://msdn.microsoft.com/en-us/library/windows/desktop/aa375496(v=vs.85).aspx" rel="nofollow noreferrer">BCryptSecretAgreement</a> API, which returns me the pre-shared key secret handle (BCRYPT_SECRET_HANDLE). 

How can I export the pre-shared key as BYTE array from the BCRYPT_SECRET_HANDLE?

Exporting shared secret as BYTE array from BCRYPT_SECRET_HANDLE

Windows Server

对称加密

Windows

我正在使用加密的下一代API (CNG)实现ECDHE。我成功生成了公钥和私钥。对于预共享密钥，我使用接口，它会返回预共享密钥秘密句柄 (BCRYPT_SECRET_HANDLE)。如何从BCRYPT_SECRET_HANDLE中导出预共享密钥为字节数组？

问从BCRYPT_SECRET_HANDLE中将共享密钥导出为字节数组
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