Encryption Decryption Question:

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Intuitively, we might expect that by encrypting a message twice with some block cipher, either with the same key or by using two different keys, then we would expect the resultant encryption to be stronger in all but some exceptional circumstances. And by using three encryptions, we would expect to achieve a yet greater level of security. While there are some more complicated issues to consider, this is pretty much the case, and triple-DES has been used for a considerable time as a more secure cipher for protecting the keys used with single-DES. However, there are some surprising results when we consider exactly how much additional protection is provided by using double and triple encryption.