Explanation

Box 1: var key = await Resolver.ResolveKeyAsyn(keyBundle,KeyIdentifier.CancellationToken.None); Box 2: var x = new BlobEncryptionPolicy(key,resolver); Example:
// We begin with cloudKey1, and a resolver capable of resolving and caching Key Vault secrets.
BlobEncryptionPolicy encryptionPolicy = new BlobEncryptionPolicy(cloudKey1, cachingResolver); client.DefaultRequestOptions.EncryptionPolicy = encryptionPolicy; Box 3: cloudblobClient. DefaultRequestOptions.EncryptionPolicy = x; References:
https://github.com/Azure/azure-storage-net/blob/master/Samples/GettingStarted/EncryptionSamples/KeyRotatio