Initial Commit

en/decipher function has been loosely coded, as well as a function to permute bits using a vector

Author: Matt Manzi

.gitignore

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+.DS_Store
+/.build
+/Packages
+/*.xcodeproj
+xcuserdata/
+.swiftpm/xcode/package.xcworkspace/contents.xcworkspacedata

Package.swift

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+// swift-tools-version:5.1
+// The swift-tools-version declares the minimum version of Swift required to build this package.
+
+import PackageDescription
+
+let package = Package(
+    name: "s-des",
+    dependencies: [
+        // Dependencies declare other packages that this package depends on.
+        // .package(url: /* package url */, from: "1.0.0"),
+    ],
+    targets: [
+        // Targets are the basic building blocks of a package. A target can define a module or a test suite.
+        // Targets can depend on other targets in this package, and on products in packages which this package depends on.
+        .target(
+            name: "s-des",
+            dependencies: []),
+        .testTarget(
+            name: "s-desTests",
+            dependencies: ["s-des"]),
+    ]
+)

README.md

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+# s-des
+
+A description of this package.

Sources/s-des/main.swift

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+//
+//  main.swift
+//  S-DES algorithm command-line entry point.
+//
+//  Created by Matt Manzi on 2/25/20.
+//  Project 2 of CMSC 487, Spring 2020.
+//

Sources/s-des/s_des.swift

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+//
+//  s_des.swift
+//  Houses all the core functionality of the Simplified Data Encryption Standard (DES).
+//
+//  Created by Matt Manzi on 2/25/20.
+//  Project 2 of CMSC 487, Spring 2020.
+//
+
+import Foundation
+
+let ROUNDS = 4
+let IP: [[UInt8]] = [
+    [2, 6, 3, 1, 4, 8, 5, 7],
+    [4, 1, 3, 5, 7, 2, 8, 6]
+]
+
+/**
+ TODO: comment
+ */
+func cipher(_ block: UInt8, using key: UInt16) -> UInt8 {
+    
+    // initial permutation
+    let permuted = permute(block, by: IP[0])
+    
+    /*
+     split block into L and R, like:
+         MSb                   LSb
+         +-----------+-----------+
+         |     r     |     l     |
+         +-----------+-----------+
+     */
+    var l: UInt8 = (permuted & 0x0F)
+    var r: UInt8 = (permuted & 0xF0) >> 4
+    
+    // perform cipherment rounds
+    for i in 0..<ROUNDS {
+        
+        let k = ks(i + 1, key)
+        
+        let temp = l ^ f(r, k)
+        l = r
+        r = temp
+        
+    }
+    
+    /*
+     combine L and R into single block, like:
+         MSb                   LSb
+         +-----------+-----------+
+         |     l     |     r     |
+         +-----------+-----------+
+     */
+    let preoutput: UInt8 = (l << 4) + r
+    
+    // inverse initial permutation
+    let output = permute(preoutput, by: IP[1])
+    
+    return output
+}
+
+/**
+ TODO: comment
+ */
+func permute<T: UnsignedInteger>(_ bits: T, by vector: [T]) -> T {
+    
+    // isolate each bit and move it to it's permutated position
+    var permuted: T = 0
+    for (i, bit) in vector.enumerated() {
+        let mask: T = 1 << (bit - 1)
+        let shift = (i + 1) - Int(bit)
+        permuted += (bits & mask) << shift
+    }
+    
+    return permuted
+}
+
+/**
+ TODO: implement
+ */
+func ks(_ round: Int, _ key: UInt16) -> UInt8 {
+    
+    return 0
+}
+
+/**
+ TODO: implement
+ */
+func f(_ halfBlock: UInt8, _ k: UInt8) -> UInt8 {
+    
+    return 0
+}

Tests/LinuxMain.swift

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+import XCTest
+
+import s_desTests
+
+var tests = [XCTestCaseEntry]()
+tests += s_desTests.allTests()
+XCTMain(tests)

Tests/s-desTests/XCTestManifests.swift

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+import XCTest
+
+#if !canImport(ObjectiveC)
+public func allTests() -> [XCTestCaseEntry] {
+    return [
+        testCase(s_desTests.allTests),
+    ]
+}
+#endif

Tests/s-desTests/s_desTests.swift

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+import XCTest
+import class Foundation.Bundle
+
+final class s_desTests: XCTestCase {
+    func testExample() throws {
+        // This is an example of a functional test case.
+        // Use XCTAssert and related functions to verify your tests produce the correct
+        // results.
+
+        // Some of the APIs that we use below are available in macOS 10.13 and above.
+        guard #available(macOS 10.13, *) else {
+            return
+        }
+
+        let fooBinary = productsDirectory.appendingPathComponent("s-des")
+
+        let process = Process()
+        process.executableURL = fooBinary
+
+        let pipe = Pipe()
+        process.standardOutput = pipe
+
+        try process.run()
+        process.waitUntilExit()
+
+        let data = pipe.fileHandleForReading.readDataToEndOfFile()
+        let output = String(data: data, encoding: .utf8)
+
+        XCTAssertEqual(output, "Hello, world!\n")
+    }
+
+    /// Returns path to the built products directory.
+    var productsDirectory: URL {
+      #if os(macOS)
+        for bundle in Bundle.allBundles where bundle.bundlePath.hasSuffix(".xctest") {
+            return bundle.bundleURL.deletingLastPathComponent()
+        }
+        fatalError("couldn't find the products directory")
+      #else
+        return Bundle.main.bundleURL
+      #endif
+    }
+
+    static var allTests = [
+        ("testExample", testExample),
+    ]
+}