Secure Hash Algorithms…
Comparison of Message Digest Algorithms
In addition to the SHA family, other common hashing algorithms like MD5 and BLAKE2 offer different performance/security tradeoffs.
MD5 Hashing
Introduced in 1991 through RFC 1321, MD5 pioneered cryptographic hashing for verifying data integrity. Due to collisions found in SHA-1, MD5 is also considered insecure for collision resistance. However it remains very widely used for error checking due to performance:
Security Level – Unsafe for cryptographic use. Trivial to intentionally generate collisions.
Hash Length – 128 bit digest
Performance – Very fast, roughly 2x the speed of SHA-256 in benchmarks.
Use Cases – Non-cryptographic error checking. Still default in tools like OpenSSL for legacy reasons.
BLAKE2b Hashing
BLAKE2 is a recent hash algorithm focused on speed while maintaining a security margin. BLAKE2b optimized for 64-bit platforms roughly matches SHA-512 performance while offering higher resistance to length extension attacks.
Security Level – Comparable to SHA-2 family for collision resistance.
Hash Length – Up to 512 bits.
Performance – Faster than SHA-512 in benchmarks.
Use Cases – Modern alternative to SHA-2/SHA-3 gaining adoption in cryptography focused applications.
Here is an example benchmark hashing a 4GB file using various algorithms on an Intel Linux server:
| Hash | Speed | Security Level |
|---|---|---|
| MD5 | 850 MB/sec | Broken/Unsafe |
| SHA-256 | 375 MB/sec | Strong |
| BLAKE2b | 550 MB/sec | Strong |
| SHA3-512 | 280 MB/sec | Very Strong |
So while dated algorithms like MD5 offer blazing speed, modern hashes like SHA-256 and BLAKE2b resist attacks with reasonable efficiency tradeoffs.
Underlying Math of SHA-256
SHA-256 relies on sophisticated mathematical constructions that enable quickly calculating a seemingly random hash. Underlying foundations include:
Merkle-Damgård Construction – Scheme to repeatedly hash chunks of input in a streaming fashion allowing arbitrary length messages.
Compression Function – Core hash algorithm mixing previous chain value with next message chunk. Utilizes bitwise operations, modular addition, and XORs.
Constants – Initial fixed hash values and round constants derived from the square roots of primes. Provide starting state and asymmetry.
Message Scheduling – Message gets parsed into 32 bit blocks then expanded to 64 bits per round function.
The SHA-256 compression function utilizes a sequence of 64 rounds interspersed with modular additions and XORs to chain together the hash output. This structured pseudorandom design enables very efficient calculation via bitwise CPU operations.
Hardware implementations can further accelerate hashing using parallelization and vector instructions…
Hardware Accelerated Hashing
While hash calculations rely purely on mathematical operations, modern CPU design allows massively parallelizing algorithms like SHA-256 by processing on multiple data chunks simultaneously.
Intel SHA Extensions specifically target speeding up SHA rounds through SIMD registers and instructions including:
- Vectorization – Compute 4 SHA rounds simultaneously per 256 bit YMM register.
- Multiline Compression – Each core handles 4 parallel hash streams.
- Reduced Instructions – New variable length SHA opcode support.
Here is an example benchmark on an IntelCascade Lake server hastening an 8GB file:
| Hash Method | Speed | Computation Gain |
|---|---|---|
| SHA256 Software | 550 MB/s | 1x |
| SHA256 NiNi | 3.1 GB/s | 5.6x |
So properly optimized software utilizing SHA-NI can provide over 5x gains through parallelization!
BTC mining rigs also leverage custom ASICs with SHA accelerators achieving vast improvements for brute forcing block hashes. As hash complexity grows, expect further hardware optimization playing crucial roles.
Exploring the SHA-3 Standard
Most security experts consider the SHA-2 algorithms strong enough to resist attack for the foreseeable future. However, the SHA-3 standard based on the Keccak algorithm provides an extra hedge against the unknown:
Design – SHA-3 utilizes a significantly different sponge construction based on permutation cipher Keccak. This provides an alternative to hash vulnerabilities relying merely on different mathematical assumptions.
Performance – Roughly 2-5x slower than SHA-2 depending on digest size chosen. Throughput ranges from about half to one-third the speed.
Adoption – Seeing growing support across cryptographic applications and protocols, especially in cases like post-quantum cryptography concerned with future attack capabilities.
The Keccak permutation utilizes 1600 bits of state arranged in a 3-dimensional sponge structure. This undergoes 24 rounds of mixing utilizing 5 basis operations: XOR, AND, rotation, permutation, translation. By relying on wholly different primitives and constructions, SHA-3 adds diversity guarding against theoretical weaknesses in SHA-2.
Here is an example of SHA3-256 hashing on the command line:
$ echo "hello world" | sha3sum -a 256
36f028580bb02cc8272a9a020f4200e346e276ae664e45ee80745574e2f5ab80So while migrating from SHA-2 is not urgently needed, SHA-3 adoption provides additional assurance as a robust hashing fallback…
Signing Git Commits with SHA-1
The git version control system heavily leverages SHA-1 hashes to authenticate history by cryptographically signing commits:
$ git commit -S -m "Commit message"This utilizes GPG and your private key to attach a signature hash to the commit stored in the blockchain ledger. The SHA-1 hash gets recomputed at each commit point allowing detecting any tampered change:
$ git show --show-signature
commit f7cf3ca31a5ba7d11c37072a35810c2e32e4c38e
gpg: Signature made Fri Apr 2 12:56:25 2021 EDT
gpg: using RSA key 7ED16053
gpg: Good signature from "Example <user@email.com>" [ultimate]
...Anyone can transparently verify commits have not been altered by checking the attached cryptographic SHA-1 hash matches signing key. This provides non-repudiation assurances essential to decentralized teams.
For sensitive projects demanding irrefutable integrity, SHA guarded git commits are crucial. The distributed model eliminates central point failure for protecting entire code history.
Conclusion
From verifying file downloads to securing decentralized blockchains, Secure Hashing Algorithms permeate software infrastructure providing vital protection. This guide has covered both theoretical foundations and practical command line usage of SHA checksums within Linux.
Be sure to leverage published SHA sums from open source projects or distribution mirror sites to guarantee integrity of critical packages. Properly salted password hashing remains essential for resisting crack attempts in case of database compromise. For assured non-repudiation, sign git commits within sensitive repositories.
Reach out if you have any other questions regarding adoption of SHA cryptography techniques!