This repository contains the experiments for expectation cryptanalysis on round-reduced AES and its small-scale version [CMR05].

This implementation supports 128 and 256 bit keys. secworks/aes. Verilog implementation of the symmetric block cipher AES (Advanced Encryption Standard) as specified in NIST FIPS 197. This implementation supports 128 and 256 bit keys. secworks/aes. // The AES key memory including round key generator. // // // Author: Joachim Strombergson. Assist in expanding the AES cipher key, by computing steps towards generating a round key for encryption, using 128-bit data specified in the source operand and an 8-bit round constant specified as an immediate, store the result in the destination operand. The destination operand is an XMM register. Based on Rijindael’s AES theory, we divided the functions into encoding and transcoding. The operation module for both parts is shown in Table 1 (each module is described in later sections). The generation of the S-Box form (see “Implementation Method” for more information) is the key to using AES theory. Such a step is easily reversed by another exclusive-or of the same key with the ciphertext. In the case of the AES, there are a number of rounds, each needing its own key, so the actual key is ``stretched out' and transformed to give portions of key for each round. This is the key expansion that is the topic of this section. I am reading over a slide that I found online regarding the DES algorithm for encryption and I am a little confused about the per round key generation. From the slide below, I understand that each per round key is obtained by shifting left either 1 or 2 bits depending on the round.

Contents

The directory contains several C++ implementations. Some represent distinguishers, others are functional tests to verify our implementations.

Distinguishers

Key Generator Download

  • tests/test_five_round_distinguisher_small.ccThe five-round expectation distinguisher on Small-AES that starts from $delta$-sets of $2^8$ values of a single byte and counts the number of pairs that collide in at least one inverse diagonal after almost five rounds (the final MixColumns operation is neglected).

  • tests/test_five_round_non_delta_set_test.ccTests a randomness assumption as preparation step of the six-round expectation distinguisher on Small-AES. Given a structure of $2^{16} - binom{2^4}{2}$ texts that iterate over all values of a column, tests all pairs that are active in more than one byte at the beginning and counts the number of pairs that collide in at least one inverse diagonal after almost five rounds (the final MixColumns operation is neglected).

  • tests/test_five_round_single_byte_distinguisher.ccA test of a five-round distinguisher for the AES that tries to count the number of collisions in a single byte after five rounds. This produced no senseful result.

  • tests/test_five_round_single_byte_distinguisher_small.ccA test of a five-round distinguisher for the Small-AES that tries to count the number of collisions in a single byte after five rounds. In experiments, it produced a multiple-of-4 property, which did not occur for the real AES, as illustrated in the test test_five_round_single_byte_distinguisher.

  • tests/test_four_round_distinguisher_small.ccThe four-round expectation distinguisher on Small-AES.

  • tests/test_four_round_id_distinguisher.ccThe four-round impossible-differential distinguisher on Small-AES.

  • tests/test_six_round_distinguisher_prp.ccThe (six-round-AES) expectation distinguisher with full Speck-64-96 for verification of the PRP behavior to find differences with test_six_round_distinguisher_small. Given a structure of $2^{16}$ texts that iterate over all values of a diagonal, counts the number of pairs that collide in at least one column.

  • tests/test_six_round_distinguisher_small.ccThe six-round expectation distinguisher on Small-AES. Given a structure of $2^{16}$ texts that iterate over all values of a diagonal, counts the number of pairs that collide in at least one column after almost five rounds (the final MixColumns and ShiftRows operations are neglected. Therefore, the program compares columns and not anti-diagonals).

  • tests/test_six_round_key_recovery_small.ccThe six-round expectation key-recovery attack on Small-AES. Extends test_five_round_distinguisher_small by a key-recovery phase. Given a structure of $2^{16}$ texts that iterate over all values of a diagonal, counts the number of pairs that collide in at least one inverse diagonal after almost five rounds (the final MixColumns operation is neglected). Outputs the $16$-bit keys in descending order of their counters.

Usage

The distinguishers provide a command-line interface for parameters, usually, the number of tested keys, number of plaintext sets per key. In some cases, a parameter also distinguishes whether the investigated cipher or a pseudo-random permutation shall be used.Note the small argument parser shows only the long-string names for the options. Usually, you can also write single-character arguments k for the number of keys, s for the number of sets (attention: sometimes, their number is asked as the power of two, so that $4$ means $2^4 = 16$), and r, where r 1 means use the pseudo-random primitive, and r 0 means to use the non-random (real) primitive.For example, the following call runs the expectation distinguisher with $2^4$ keys on $100$ random keys each with the pseudo-random primitive:

Functional Tests

The functional test verify the implementation of the used primitives---here AES-128, Small-AES, and Speck-64---as well as utilities that serve useful in our distinguishers:

  • tests/test_aes128.cc
  • tests/test_small_aes.cc
  • tests/test_speck64.cc
  • tests/test_utils.cc
  • tests/test_hash_table_generator.cc

Our implementations of the AES and Small-AES employ AES-NI and AVX instruction sets for better performance. These processor features are usually supported if they are listed in

cat /proc/cpuinfo grep aes

Replace aes by avx to see if AVX instructions are supported.

Build

A CMakeLists.txt file is shipped that should allow you to build the tests above, if CMake, a C++ compiler, and GTest are installed.

In the root directory, type cmake . in a commandline/shell to build a make file. Thereupon, you can build the individual targets with make <target> where <target> is e.g., test_five_round_distinguisher_small, or build all by typing make all.

Executables will be placed in the directory bin.

Dependencies

  • cmake for building.
  • g++ or clang++ as standard compiler. This can be customized in the CMakeLists.txt file.
  • gtest: Google's unit test framework for the functional tests.
  • pthreads: Needed by gtest.

References

[CMR05] Carlos Cid, Sean Murphy, and Matthew J. B. Robshaw. Small Scale Variants of the AES. In Henri Gilbert and Helena Handschuh, editors, FSE, volume 3557 of Lecture Notes in Computer Science, pages 145–162. Springer, 2005.

Advanced Encryption Standard(AES) is a symmetric encryption algorithm. AES is the industry standard as of now as it allows 128 bit, 192 bit and 256 bit encryption.Symmetric encryption is very fast as compared to asymmetric encryption and are used in systems such as database system. Following is an online tool to generate AES encrypted password and decrypt AES encrypted password. It provides two mode of encryption and decryption ECB and CBC mode. For more info on AES encryption visit this explanation on AES Encryption.

Also, you can find the sample usage screenshot below:

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Usage Guide

Aes 128 key generator

Any plain-text input or output that you enter or we generate is not stored on this site, this tool is provided via an HTTPS URL to ensure that text cannot be stolen.

For encryption, you can either enter the plain text, password, an image file or a .txt file that you want to encrypt. Now choose the block cipher mode of encryption. ECB(Electronic Code Book) is the simplest encryption mode and does not require IV for encryption. The input plain text will be divided into blocks and each block will be encrypted with the key provided and hence identical plain text blocks are encrypted into identical cipher text blocks. CBC mode is highly recommended and it requires IV to make each message unique. If no IV is entered then default will be used here for CBC mode and that defaults to a zero based byte[16].

The AES algorithm has a 128-bit block size, regardless of whether you key length is 256, 192 or 128 bits. When a symmetric cipher mode requires an IV, the length of the IV must be equal to the block size of the cipher. Hence, you must always use an IV of 128 bits (16 bytes) with AES.

AES provides 128 bit, 192 bit and 256 bit of secret key size for encryption. Things to remember here is if you are selecting 128 bits for encryption, then the secret key must be of 16 bits long and 24 and 32 bits for 192 and 256 bits of key size. Now you can enter the secret key accordingly. By default, the encrypted text will be base64 encoded but you have options to select the output format as HEX too.

Similarly, for image and .txt file the encrypted form will be Base64 encoded.

Generator

S-aes Round Key Generator For Sale

Below is a screenshot that shows a sample usage of this online AES encryption tool.

AES decryption has also the same process. By default it assumes the entered text be in Base64. The input can be Base64 encoded or Hex encoded image and .txt file too. And the final decrypted output will be Base64 string. If the intended output is a plain-text then, it can be decoded to plain-text in-place.

But if the intended output is an image or .txt file then you can use this tool to convert the base64 encoded output to an image.

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