Working implementation of encrypt and decrypt

Cargo.lock

@@ -120,10 +120,11 @@ checksum = "2304e00983f87ffb38b55b444b5e3b60a884b5d30c0fca7d82fe33449bbe55ea"
 
 [[package]]
 name = "idea"
-version = "0.1.0"
+version = "0.2.0"
 dependencies = [
  "clap",
  "clap-num",
+ "modinverse",
 ]
 
 [[package]]
@@ -132,6 +133,24 @@ version = "1.70.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f8478577c03552c21db0e2724ffb8986a5ce7af88107e6be5d2ee6e158c12800"
 
+[[package]]
+name = "modinverse"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2f62f577f148cc1a9466e7065a22e59466a7d537cceba5e77e57181d0f706633"
+dependencies = [
+ "num-integer",
+]
+
+[[package]]
+name = "num-integer"
+version = "0.1.46"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7969661fd2958a5cb096e56c8e1ad0444ac2bbcd0061bd28660485a44879858f"
+dependencies = [
+ "num-traits",
+]
+
 [[package]]
 name = "num-traits"
 version = "0.2.19"

Cargo.toml

@@ -1,8 +1,9 @@
 [package]
 name = "idea"
-version = "0.2.0"
+version = "1.0.0"
 edition = "2021"
 
 [dependencies]
 clap = { version = "4.0", features = ["derive"] }
 clap-num = { version = "1.1" }
+modinverse = { version = "0.1" }

src/main.rs

@@ -1,9 +1,8 @@
-// Angefangen: 13:30
-// bis: 16:20
-//
+// ca 5h
 
 use clap::Parser;
 use clap_num::maybe_hex;
+use modinverse::modinverse;
 
 #[derive(Parser)]
 struct Cli {
@@ -55,7 +54,6 @@ fn derive_keys(mut k: u128) -> Vec<Keys> {
         subkeys.push(((k >> 96) & 0xFFFF) as u16);
         subkeys.push(((k >> 112) & 0xFFFF) as u16);
         k = k.rotate_left(25);  
-        println!("key after shift {k}");
     }
     let mut i = 0;
     while keys.len() < 8 {
@@ -71,8 +69,8 @@ fn derive_keys(mut k: u128) -> Vec<Keys> {
 }
 
 fn add(a: u16, b: u16) -> u16 {
-    let (a, b, m) = (a as u32, b as u32, 0x10000 as u32);
-    ((a * b) % m) as u16
+    let (a, b, m) = (a as i32, b as i32, 0x10000 as i32);
+    ((a + b) % m) as u16
 }
 
 fn mul(a: u16, b: u16) -> u16 {
@@ -90,26 +88,101 @@ fn mul(a: u16, b: u16) -> u16 {
     }
 }
 
-fn idea_round() -> Vr {
-    Vr::split(80)    
+fn idea_round(ks: &Keys, xs: Vr) -> Vr {
+    let u1 = mul(ks.z1, xs.v1);
+    let u2 = mul(ks.z2, xs.v2);
+    let u3 = add(ks.z3, xs.v3);
+    let u4 = add(ks.z4, xs.v4);
+    let u13 = u1 ^ u3;
+    let u24 = u2 ^ u4;
+    let u5 = mul(ks.z5, u13);
+    let c1 = mul(ks.z6, add(u24, u5));
+    let c2 = add(u5, c1);
+    Vr { v1: c1 ^ u3, v2: c2 ^ u4, v3: c1 ^ u1, v4: c2 ^ u2 }   
+}
+
+fn idea_finish(ks: &Keys, xs: Vr) -> Vr {
+    let u1 = mul(ks.z1, xs.v1);
+    let u2 = mul(ks.z2, xs.v2);
+    let u3 = add(ks.z3, xs.v3);
+    let u4 = add(ks.z4, xs.v4);
+    Vr { v1: u1, v2: u2, v3: u3, v4: u4 } 
+}
+
+fn invert_keys(ks: &Keys, z5: u16, z6: u16) -> Keys {
+    let mut z1 = ks.z1 as i32;
+    let mut z2 = ks.z2 as i32;
+    if ks.z1 == 0 {
+        z1 = 0x010000 as i32;
+    }
+    if ks.z2 == 0 {
+        z2 = 0x010000 as i32;
+    }
+    Keys {
+    z1: modinverse(z1 as i32, 0x0010001 as i32).expect("Modular inverse of z1 doesn't exist!") as u16,
+    z2: modinverse(z2 as i32, 0x0010001 as i32).expect("Modular inverse of z2 doesn't exist!") as u16,
+    z3: (0x10000 as u32 - ks.z3 as u32) as u16,
+    z4: (0x10000 as u32 - ks.z4 as u32) as u16,
+    z5: z5,
+    z6: z6 }
 }
 
 fn encrypt(k: u128, m: u64) -> u64 {
     let xr = Vr::split(m);
     assert_eq!(m, xr.expand());
-    let round_keys = derive_keys(k);
-    mul(xr.v1, 0).into()
+    // Derive keys
+    let kr = derive_keys(k);
+
+    let mut bs = xr;
+    let mut i = 0;
+    while i < 8 {
+        println!("Round {i}:");
+        bs = idea_round(&kr[i], bs);
+        println!("intermediate result: {:?}\n", bs.expand());
+        i = i+1;
+    }
+    let ys = idea_finish(&kr[8], bs);
+    ys.expand()
+}
+
+fn decrypt(k: u128, m: u64) -> u64 {
+    let xr = Vr::split(m);
+    assert_eq!(m, xr.expand());
+    // Derive and invert keys
+    let kr = derive_keys(k);
+    let mut dr: Vec<Keys> = Vec::new();
+    let mut i = 8;
+    while i > 0 {
+        let ds = invert_keys(&kr[i], kr[i-1].z5, kr[i-1].z6);
+        i = i-1;
+        dr.push(ds);
+    }
+    let ds = invert_keys(&kr[0], 0, 0);
+    dr.push(ds);
+
+    let mut bs = xr;
+    while i < 8 {
+        println!("Round {i}:");
+        bs = idea_round(&dr[i], bs);
+        println!("intermediate result: {:?}\n", bs.expand());
+        i = i+1;
+    }
+    let ys = idea_finish(&dr[8], bs);
+    ys.expand()
 }
 
 fn main() {
-    println!("Welcome to your IDEA encryption tool!");
+    println!("Welcome to your IDEA encryption tool!\n");
 
     let args = Cli::parse();
     let key: u128 = args.key;
+    let key2: u128 = args.key;
     let message: u64 = args.message;
 
-    println!("message: {:?}, key: {:?}", message, key);
+    println!("message: {:?}, key: {:?}\n", message, key);
 
     let cipher: u64 = encrypt(key, message);
-    println!("ciphertext: {:?}", cipher);
+    println!("Ciphertext: {:?}\n", cipher);
+    let plain: u64 = decrypt(key2, cipher);
+    println!("Computed plaintext: {:?}", plain);
 }