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In cryptography, Galois/Counter Mode (GCM) [1] is a mode of operation for symmetric-key cryptographic block ciphers which is widely adopted for its performance. GCM throughput rates for state-of-the-art, high-speed communication channels can be achieved with inexpensive hardware resources.
AES-GCM-SIV is an improvement over the very similarly named algorithm GCM-SIV, with a few very small changes (e.g. how AES-CTR is initialized), but which yields practical benefits to its security "This addition allows for encrypting up to 2 50 messages with the same key, compared to the significant limitation of only 2 32 messages that were ...
AES speed at 128, 192 and 256-bit key sizes. [clarification needed] [citation needed] Rijndael is free for any use public or private, commercial or non-commercial. [1] The authors of Rijndael used to provide a homepage [2] for the algorithm. Care should be taken when implementing AES in software, in particular around side-channel attacks.
Table compares implementations of block ciphers. Block ciphers are defined as being deterministic and operating on a set number of bits (termed a block) using a symmetric key. Each block cipher can be broken up into the possible key sizes and block cipher modes it can be run with.
Like Galois/Counter Mode, AES-GCM-SIV combines the well-known counter mode of encryption with the Galois mode of authentication. The key feature is the use of a synthetic initialization vector (SIV) which is computed with Galois field multiplication using a construction called POLYVAL (a little-endian variant of Galois/Counter Mode's GHASH).
An AES instruction set includes instructions for key expansion, encryption, and decryption using various key sizes (128-bit, 192-bit, and 256-bit). The instruction set is often implemented as a set of instructions that can perform a single round of AES along with a special version for the last round which has a slightly different method.
The key space increases by a factor of 2 for each additional bit of key length, and if every possible value of the key is equiprobable; this translates into a doubling of the average brute-force key search time with every additional bit of key length. This implies that the effort of a brute-force search increases exponentially with key length.
The Advanced Encryption Standard uses a key schedule to expand a short key into a number of separate round keys. The three AES variants have a different number of rounds. Each variant requires a separate 128-bit round key for each round plus one more. [note 1] The key schedule produces the needed round keys from the initial key.