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Block cipher is one of the most widely-used tool in cryptography, and its mode of operation features the use of a symmetric-key block-cipher algorithm in providing information security such as confidentiality or authenticity. Five modes of operation with AES algorithm will be discussed in this paper: Electronic Codebook (ECB), Cipher Block Chaining (CBC), Cipher Feedback (CFB), Output Feedback (OFB), and Counter (CTR). These modes can provide cryptographic protection for sensitive, but classified, computer data.
Keywords: Computer security; cryptography; block cipher; mode of operation