From b4e92550b086a8a75a4470135dfd0ed30a81f0bb Mon Sep 17 00:00:00 2001 From: nktrejo2020 <69374108+nktrejo2020@users.noreply.github.com> Date: Mon, 21 Sep 2020 15:05:09 -0700 Subject: [PATCH] Update block-ciphers.rst --- src/block-ciphers.rst | 34 +++++++++++++++++----------------- 1 file changed, 17 insertions(+), 17 deletions(-) diff --git a/src/block-ciphers.rst b/src/block-ciphers.rst index d50cdf38..fe0e7820 100644 --- a/src/block-ciphers.rst +++ b/src/block-ciphers.rst @@ -166,23 +166,23 @@ The most common block cipher in current use is AES. Contrary to its predecessor DES (which we'll look at in more detail in the next chapter), AES was selected through a public, peer-reviewed -competition following an open call for proposals. This competition -involved several rounds where all of the contestants were presented, +competition that arose from an open call for proposals. The competition +involved several rounds of contestant presentations, subject to extensive cryptanalysis, and voted upon. The AES process was -well-received among cryptographers, and similar processes are generally -considered to be the preferred way to select cryptographic standards. +well-received among cryptographers. Similar processes are preferred +for selecting cryptographic standards. Prior to being chosen as the Advanced Encryption Standard, the algorithm was known as Rijndael, a name derived from the two last names of the Belgian cryptographers that designed it: Vincent Rijmen and Joan Daemen. -The Rijndael algorithm defined a family of block ciphers, with block -sizes and key sizes that could be any multiple of 32 bits between 128 -bits and 256 bits. :cite:`daemen:aes` When Rijndael became +The Rijndael algorithm defined a family of block ciphers. The block +sizes and key sizes could be any multiple of 32 bits between 128 +bits to 256 bits. :cite:`daemen:aes` When Rijndael became AES through the FIPS standardization process, the parameters were restricted to a block size of 128 bits and keys sizes of 128, 192 and 256 bits. :cite:`fips:aes` -There are no practical attacks known against AES. While there have been +No practical attacks exist against AES. While there have been some developments in the last few years, most of them involve related-key attacks :cite:`cryptoeprint:2009:317`, some of them only on reduced-round versions of AES @@ -195,24 +195,24 @@ them only on reduced-round versions of AES easier to attack. These attacks can give insight as to how resistant the full cipher is. - A related key attack involves making some predictions about how AES - will behave under several different keys with some specific - mathematical relation. These relations are fairly simple, such as + A related key attack involves predicting how AES + behaves under different keys with specific + mathematical relations. These relations are fairly simple, such as XORing with an attacker-chosen constant. If an attacker is allowed to encrypt and decrypt a large number of blocks with these related keys, they can attempt to recover the original key with significantly less computation than would ordinarily be necessary to crack it. - While a theoretically ideal block cipher wouldn't be vulnerable to a - related key attack, these attacks aren't considered practical + While a theoretically, ideal block cipher would not be vulnerable to a + related key attack, these attacks are not considered practical concerns. In practice cryptographic keys are generated via a cryptographically secure pseudorandom number generator, or a - similarly secure :term:`key agreement` scheme or key derivation scheme (we'll + similarly secure :term:`key agreement` scheme, or a key derivation scheme (we'll see more about those later). Therefore, the odds of selecting two such related keys by accident is nonexistent. These attacks are - interesting from an academic perspective: they can help provide - insight in the workings of the cipher, guiding cryptographers in - designing future ciphers and attacks against current ciphers. + interesting from an academic perspective: they provide + insight in the workings of the cipher, guiding cryptographers in the + design of future ciphers and attacks against current ciphers. A closer look at Rijndael ^^^^^^^^^^^^^^^^^^^^^^^^^