commit cb5fb46373cc085459dcc3658b53c49f4186eaca
Author: mehbark <terezi@pyrope.net>
Date:   Thu Apr 17 10:31:10 2025 -0400

    initial bruteforce attempt

diff --git a/Cargo.lock b/Cargo.lock
new file mode 100644
index 0000000..05085de
--- /dev/null
+++ b/Cargo.lock
@@ -0,0 +1,93 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "block-buffer"
+version = "0.10.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3078c7629b62d3f0439517fa394996acacc5cbc91c5a20d8c658e77abd503a71"
+dependencies = [
+ "generic-array",
+]
+
+[[package]]
+name = "capitalization-collision"
+version = "0.1.0"
+dependencies = [
+ "sha1",
+]
+
+[[package]]
+name = "cfg-if"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
+
+[[package]]
+name = "cpufeatures"
+version = "0.2.17"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "59ed5838eebb26a2bb2e58f6d5b5316989ae9d08bab10e0e6d103e656d1b0280"
+dependencies = [
+ "libc",
+]
+
+[[package]]
+name = "crypto-common"
+version = "0.1.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1bfb12502f3fc46cca1bb51ac28df9d618d813cdc3d2f25b9fe775a34af26bb3"
+dependencies = [
+ "generic-array",
+ "typenum",
+]
+
+[[package]]
+name = "digest"
+version = "0.10.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9ed9a281f7bc9b7576e61468ba615a66a5c8cfdff42420a70aa82701a3b1e292"
+dependencies = [
+ "block-buffer",
+ "crypto-common",
+]
+
+[[package]]
+name = "generic-array"
+version = "0.14.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "85649ca51fd72272d7821adaf274ad91c288277713d9c18820d8499a7ff69e9a"
+dependencies = [
+ "typenum",
+ "version_check",
+]
+
+[[package]]
+name = "libc"
+version = "0.2.172"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d750af042f7ef4f724306de029d18836c26c1765a54a6a3f094cbd23a7267ffa"
+
+[[package]]
+name = "sha1"
+version = "0.10.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e3bf829a2d51ab4a5ddf1352d8470c140cadc8301b2ae1789db023f01cedd6ba"
+dependencies = [
+ "cfg-if",
+ "cpufeatures",
+ "digest",
+]
+
+[[package]]
+name = "typenum"
+version = "1.18.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1dccffe3ce07af9386bfd29e80c0ab1a8205a2fc34e4bcd40364df902cfa8f3f"
+
+[[package]]
+name = "version_check"
+version = "0.9.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0b928f33d975fc6ad9f86c8f283853ad26bdd5b10b7f1542aa2fa15e2289105a"
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..4d8cc7f
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,7 @@
+[package]
+name = "capitalization-collision"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+sha1 = "0.10.6"
diff --git a/src/main.rs b/src/main.rs
new file mode 100644
index 0000000..9257d75
--- /dev/null
+++ b/src/main.rs
@@ -0,0 +1,50 @@
+use std::collections::HashMap;
+
+use sha1::{Digest, Sha1};
+fn main() {
+    let src = b"the purple cow is prancing along";
+    let prefix_length = 7;
+
+    let alpha_count = src.iter().filter(|b| b.is_ascii_alphabetic()).count() as u32;
+    assert!(alpha_count <= 64);
+
+    let permutation_count = 2usize.pow(alpha_count);
+    let mut hashes = HashMap::new();
+
+    for upper_mask in perm_masks(alpha_count) {
+        if upper_mask % 100_000 == 0 {
+            eprintln!("{upper_mask}/{permutation_count}");
+        };
+        let capitalized = apply_capitalization_mask(src, upper_mask);
+        let digest = Sha1::digest(capitalized);
+        let prefix = &digest[..prefix_length];
+        if let Some(other_mask) = hashes.get(prefix) {
+            let other = apply_capitalization_mask(src, *other_mask);
+            println!(
+                "{}\n{}\n",
+                String::from_utf8_lossy(&capitalized),
+                String::from_utf8_lossy(&other)
+            );
+        }
+        hashes.insert(prefix.to_owned(), upper_mask);
+    }
+}
+
+fn apply_capitalization_mask<const N: usize>(bytes: &[u8; N], mut upper_mask: u64) -> [u8; N] {
+    let mut new = *bytes;
+    for i in 0..N {
+        if bytes[i].is_ascii_alphabetic() {
+            new[i] = if upper_mask & 1 == 1 {
+                bytes[i].to_ascii_uppercase()
+            } else {
+                bytes[i].to_ascii_lowercase()
+            };
+            upper_mask >>= 1;
+        }
+    }
+    new
+}
+
+fn perm_masks(options: u32) -> impl Iterator<Item = u64> {
+    0..(2u64.pow(options))
+}