XIP1101B from Xiphera is a balanced Intellectual Property (IP) core implementing the Advanced Encryption Standard (AES) in Counter Mode (CTR).
The Counter mode of operation effectively turns a block cipher into a stream cipher, and provides a number of advantages from an implementation point of view. These include the ability to use the same key expansion functionality and datapath for both encryption and decryption, and the possibility to parallelize the FPGA-based implementation by unrolling and pipelining.
XIP1101B has been designed for easy integration with FPGA- and ASIC-based designs in a vendor-agnostic design methodology, and the functionality of XIP1101B does not rely on any FPGA
XIP1101B encrypts  the incoming 128 bits long plaintext blocks by XORing (exclusive-OR)
them with the encrypted successive values of a counter. The counter is initialized with a 128 bits long initialization vector , which is then incremented by one after each encryption with the same secret key.
XIP1101B is a balanced version of the Counter mode of operation, and the encryption of a 128 bits long plaintext block takes ten (10) clock cycles. The key expansion —which is identical for both encryption and decryption operation —is performed on-the-fly and does not affect the throughput or latency of XIP1101B.
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Figure 1: Internal high-level block diagram of XIP1101B, encryption mode.
 The AES S-boxes can be implemented either in FPGA logic or internal memory blocks depending on the customer’s preference.
 The operation is identical in the decryption direction, where the only difference is decrypting ciphertext into plaintext.
 The initialization vector consists of a 32 bits long nonce, and a 96 bits long initial value.
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