RSACryptoServiceProvider.Encrypt returns "Key not valid for use in specified state" error

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Hi all,

When executing RSACryptoServiceProvider.Encrypt method (see How to generate key pairs, encrypt and decrypt data with .NET (C#) for an example), you may get a System.Security.Cryptography.CryptographicException. According to MSDN, this is to be expected in several circumstances:

The cryptographic service provider (CSP) cannot be acquired. -or-

The length of the rgb parameter is greater than the maximum allowed length. -or-

The fOAEP parameter is true and OAEP padding is not supported.

 

In my case the error message of the exception was "Key not valid for use in specified state" . Weird... Well, it took me a while to realize that this error message was certainly misleading! The key was just fine, the issue was that I was passing too many bytes to the Encrypt method! Check in MSDN the maximum length allowed by the different combinations of operating systems and padding.

I hope this helps.

Kind regards,

 

Alex (Alejandro Campos Magencio)