A stacked auto-encoder is a neural network consisting of multiple layers of sparse auto-encoders in which the outputs of each layer is wired to the inputs of the successive layer. For usefulness of stacked auto-encoders in learning, please refer to this article:
Shin, H. C., Orton, M. R., Collins, D. J., Doran, S. J., & Leach, M. O. (2012). Stacked autoencoders for unsupervised feature learning and multiple organ detection in a pilot study using 4D patient data. IEEE transactions on pattern analysis and machine intelligence, 1.
Encryption is the mathematical science of symbols, codes and secret messages. People used encryption throughout history to exchange unreadable messages (to what they hoped) by anyone other than the person intended to receive the message
Encryption is a science that uses mathematics to encrypt and decrypt data. Encryption enables you to store or transfer sensitive information over insecure networks - such as the Internet - and therefore can not be read by anyone other than the sender. As encryption is the science used to preserve the security and confidentiality of information, Cryptoanalysis is a science to break and break secure communication.