This crates implements crypto primitives which are useful for other Cosmian crypto resources

• primes: routines to extract prime numbers up to 2^400
• cs_prng: A cryptographically secure pseudo random generator that generates Big Int(s)
• brc_cprf: BRC, a constrained PRF (see below)
• aeshashmmo: using the native implementation of AES 256 as a hash function.
• timed_cache: a thread safe memory cache where items expire after a certain time
• timed_caches: a WIP. Do not use for now

It also exposes 2 traits, SymmetricCrypto and AsymmetricCrypto (aka Public Key Crypto) to which most schemes used at Cosmian are mapped. A fw of these schemes are available under the corresponding directories.

Building

Some of the encryption schemes (xChaCha20 in particular) use libsodium. These schemes are not built by default, use --feature libsodium to build them.

The default feature schemes can all be built to a WASM target.

Constrained PRF

This construct is a simple and efficient range-constrained PRF from the tree-based GGM PRF [GGM84].This instantiation has been described by Kiayiaset al.KPTZ13 and is called best range cover (BRC).

Benchmarks

Intel(R) Core(TM) i7-8700 CPU @ 3.20GHz - 6400 bogomips . Single Threaded.

Bench of leaves generation from a node with varying depth (2500 rounds per depth) Average: 76 nano per leave for depth: 4 (16 leaves) Average: 79 nano per leave for depth: 5 (32 leaves) Average: 79 nano per leave for depth: 6 (64 leaves) Average: 81 nano per leave for depth: 7 (128 leaves) Average: 80 nano per leave for depth: 8 (256 leaves) Average: 79 nano per leave for depth: 9 (512 leaves) Average: 78 nano per leave for depth: 10 (1024 leaves) Average: 78 nano per leave for depth: 11 (2048 leaves) Average: 77 nano per leave for depth: 12 (4096 leaves) Average: 77 nano per leave for depth: 13 (8192 leaves) Average: 76 nano per leave for depth: 14 (16384 leaves) Average: 77 nano per leave for depth: 15 (32768 leaves) Average: 77 nano per leave for depth: 16 (65536 leaves)

Bench of a trapdoor serialization/de-serialization averaged over 50000 rounds - 1 nodes: serialization/de-serialization 49/38 nanos) - 2 nodes: serialization/de-serialization 54/39 nanos) - 3 nodes: serialization/de-serialization 55/40 nanos) - 4 nodes: serialization/de-serialization 69/49 nanos) - 5 nodes: serialization/de-serialization 69/47 nanos) - 6 nodes: serialization/de-serialization 73/49 nanos) - 7 nodes: serialization/de-serialization 68/47 nanos) - 8 nodes: serialization/de-serialization 73/50 nanos) - 9 nodes: serialization/de-serialization 83/55 nanos) - 10 nodes: serialization/de-serialization 82/56 nanos)

AES as a Hash Function

Using the native implementation of AES 256 as a hash function.

Implements the scheme of S. Matyas, C. Meyer and J. Oseas Hᵢ = E(Hᵢ₋₁, Xᵢ)^Xᵢ^Hᵢ₋₁ where the AES encryption of plaintext X with key K will is denoted with E(K, X)

see https://www.esat.kuleuven.be/cosic/publications/article-48.pdf

Since the block size is 16 and we need to encrypt 32 bytes (top get a 256 bit hash) we use AES in counter mode to encrypt two blocks of 16 bytes

Benchmarks

The Sha256 implementation is that of libsodium. The AES MMO implementation is particularly performing for data length which are multiple of 32 bytes.

Intel(R) Core(TM) i9-9980HK CPU @ 2.40GHz - 4800 bogomips . Single Threaded.

Average over 500000 rounds of 16 data bytes: nano per hash aes: 107; sha256 325 Average over 500000 rounds of 32 data bytes: nano per hash aes: 111; sha256 326 Average over 500000 rounds of 48 data bytes: nano per hash aes: 188; sha256 323 Average over 500000 rounds of 64 data bytes: nano per hash aes: 192; sha256 629 Average over 500000 rounds of 80 data bytes: nano per hash aes: 270; sha256 628 Average over 500000 rounds of 96 data bytes: nano per hash aes: 270; sha256 624 Average over 500000 rounds of 112 data bytes: nano per hash aes: 346; sha256 623 Average over 500000 rounds of 128 data bytes: nano per hash aes: 351; sha256 885 Average over 500000 rounds of 144 data bytes: nano per hash aes: 428; sha256 887 Average over 500000 rounds of 160 data bytes: nano per hash aes: 430; sha256 885 Average over 500000 rounds of 176 data bytes: nano per hash aes: 505; sha256 886 Average over 500000 rounds of 192 data bytes: nano per hash aes: 511; sha256 1146 Average over 500000 rounds of 208 data bytes: nano per hash aes: 585; sha256 1150 Average over 500000 rounds of 224 data bytes: nano per hash aes: 592; sha256 1149 Average over 500000 rounds of 240 data bytes: nano per hash aes: 667; sha256 1147 Average over 500000 rounds of 256 data bytes: nano per hash aes: 670; sha256 1405