/// <summary>
/// Re-instantiates an <see cref="Association"/> previously persisted in a database or some
/// other shared store.
/// </summary>
/// <param name="handle">
/// The <see cref="Handle"/> property of the previous <see cref="Association"/> instance.
/// </param>
/// <param name="expires">
/// The value of the <see cref="Expires"/> property of the previous <see cref="Association"/> instance.
/// </param>
/// <param name="privateData">
/// The byte array returned by a call to <see cref="SerializePrivateData"/> on the previous
/// <see cref="Association"/> instance.
/// </param>
/// <returns>
/// The newly dehydrated <see cref="Association"/>, which can be returned
/// from a custom association store's
/// <see cref="IAssociationStore<TKey>.GetAssociation(TKey)"/> method.
/// </returns>
public static Association Deserialize(string handle, DateTime expires, byte[] privateData)
{
if (string.IsNullOrEmpty(handle))
{
throw new ArgumentNullException("handle");
}
if (privateData == null)
{
throw new ArgumentNullException("privateData");
}
expires = expires.ToUniversalTime();
TimeSpan remainingLifeLength = expires - DateTime.UtcNow;
byte[] secret = privateData; // the whole of privateData is the secret key for now.
// We figure out what derived type to instantiate based on the length of the secret.
try {
return(HmacShaAssociation.Create(secret.Length, handle, secret, remainingLifeLength));
} catch (ArgumentException ex) {
throw new ArgumentException(Strings.BadAssociationPrivateData, "privateData", ex);
}
}
internal bool IsAssociationInPermittedRange(Protocol protocol, string associationType)
{
int lengthInBits = HmacShaAssociation.GetSecretLength(protocol, associationType) * 8;
return(lengthInBits >= MinimumHashBitLength && lengthInBits <= MaximumHashBitLength);
}