System.Security.Cryptography.CryptographicException: The payload was invalid

[Jason Xu]

When you are using your .Net Core application to decrypt a string from a different machine than it was encrypted, you may run into the following exception:



Exception:

System.Security.Cryptography.CryptographicException: The payload was invalid.

at Microsoft.AspNetCore.DataProtection.Cng.CbcAuthenticatedEncryptor.DecryptImpl(Byte* pbCiphertext, UInt32 cbCiphertext, Byte* pbAdditionalAuthenticatedData, UInt32 cbAdditionalAuthenticatedData)

at Microsoft.AspNetCore.DataProtection.Cng.Internal.CngAuthenticatedEncryptorBase.Decrypt(ArraySegment`1 ciphertext, ArraySegment`1 additionalAuthenticatedData)

at Microsoft.AspNetCore.DataProtection.KeyManagement.KeyRingBasedDataProtector.UnprotectCore(Byte[] protectedData, Boolean allowOperationsOnRevokedKeys, UnprotectStatus& status)

at Microsoft.AspNetCore.DataProtection.KeyManagement.KeyRingBasedDataProtector.DangerousUnprotect(Byte[] protectedData, Boolean ignoreRevocationErrors, Boolean& requiresMigration, Boolean& wasRevoked)

at Microsoft.AspNetCore.DataProtection.KeyManagement.KeyRingBasedDataProtector.Unprotect(Byte[] protectedData)

at Microsoft.AspNetCore.DataProtection.DataProtectionCommonExtensions.Unprotect(IDataProtector protector, String protectedData)



Two things you will need to check:

1. Is the encryption key persists to a local path? - The key needs to be persisted to a shared location

2. SetApplicationName must be used to set an explicit application name. - If ApplicationName is not set, it will be generated a guid at runtime for different machines, and that will lead to the error above.





Code Example below:



services.AddDataProtection()

.ProtectKeysWithCertificate(x509Cert)

.UseCryptographicAlgorithms(

new AuthenticatedEncryptorConfiguration()

{

EncryptionAlgorithm = EncryptionAlgorithm.AES_256_CBC,

ValidationAlgorithm = ValidationAlgorithm.HMACSHA256

}

)

.PersistKeysToFileSystem(new System.IO.DirectoryInfo(Configuration.GetValue<string>("KeyLocation"))) //shared network folder for key location

.SetApplicationName("MyApplicationName")

.SetDefaultKeyLifetime(TimeSpan.FromDays(600));

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