TryParsePkcs1Decrypt Method

TryParsePkcs1Decrypt(ReadOnlySpan<Byte>, out Byte[])

Try to parse the formattedData as a PKCS #1 v1.5 block that was the result of decryption (see RFC 8017).

C#

public static bool TryParsePkcs1Decrypt(ReadOnlySpan<byte> formattedData, out byte[] outputData)

Parameters

Type	Name	Description
System.ReadOnlySpan<System.Byte>	formattedData	The data to parse.
System.Byte[]	outputData	An output argument, the method will return a new byte array containing the unpadded data portion of the block.

Returns

System.Boolean

True if the method is able to parse, false otherwise.

Remarks

This method will extract the data from the formatted data. This is generally the plaintext (the formatted data is the decrypted block). If it is successful, it will return true. If it cannot extract the information, it will return false. The caller will likely decrypt an RSA block, then try to parse it as PKCS #1 v2 OAEP. If successful, the data is collected. If not, try to parse it as PKCS #1 v1.5. Note that while unlikely, it is possible for an OAEP block to look like PKCS #1 v1.5. If you don't know which format was used, it is best to try OAEP first, and if it fails, then try PKCS #1 v1.5.

The method will verify that the first byte is 00, the second byte is 02, and that there are at least 8 padding bytes. It will then expect to find 00 and then the data to return.

Finally, the method will return a new byte array containing the actual data portion.

Because this method creates a new byte array, and it contains sensitive data, it is a good idea to overwrite the buffer when done with it.

  CryptographicOperations.ZeroMemory(outputData);

This method only supports blocks 128 or 256 bytes (1024 or 2048 bits) long.

If any element fails (the length of the formattedData is not supported, an expected byte is not there, or so on), the method will return false. If there is an error, the method might set the outputData argument to an empty array, or it might contain the purported data. If the return is false and there is data in outputData, that data is meaningless.