Played around with AES GSM no padding Encryption algorithm in .NET 4.8 and .NET 5.0. In this exercise I have encrypted and decrypted string “123456789” with base 64 encrypted key “FnAD72andADb3AtmsXRv9w==”. The encrypted string has following structure:
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Length of Nonce (4 bytes) (0,0,0,12)
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The IV/Nonce (12 bytes)
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Encrypted Ciphertext (9 bytes)
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The Tag (16 bytes) (128 bits)
In Total encryption string is byte[41] array.
For .NET 5.0 I used AesGcm class from Namespace: System.Security.Cryptography. For .NET 4.8 I used BouncyCastle NuGet package.