Testing Hashcash

Author: MattKiazyk

Xcodes/AppleAPI/Sources/AppleAPI/Hashcash.swift

@@ -0,0 +1,127 @@
+//
+//  Hashcash.swift
+//  
+//
+//  Created by Matt Kiazyk on 2023-02-23.
+//
+
+import Foundation
+import CryptoKit
+import CommonCrypto
+
+public struct Hashcash {
+
+    public func mint(resource: String,
+                     bits: UInt = 20,
+                     ext: String = "",
+                     saltCharacters: UInt = 16,
+                     stampSeconds: Bool = true,
+                     date: String? = nil) -> String? {
+        
+        let ver = "1"
+        
+        var ts: String
+        if let date = date {
+            ts = date
+        } else {
+            let formatter = DateFormatter()
+            formatter.dateFormat = stampSeconds ? "yyMMddHHmmss" : "yyMMdd"
+            ts = formatter.string(from: Date())
+        }
+        
+        let challenge = "\(ver):\(bits):\(ts):\(resource):"
+        
+        var counter = 0
+        let hexDigits = Int(ceil((Double(bits) / 4)))
+        let zeros = String(repeating: "0", count: hexDigits)
+        
+        while true {
+            guard let digest = ("\(challenge):\(counter)").sha1 else {
+                print("ERROR: Can't generate SHA1 digest")
+                return nil
+            }
+            
+            if digest.prefix(hexDigits) == zeros {
+                return "\(challenge):\(counter)"
+            }
+            counter += 1
+        }
+    }
+    
+    /**
+     Checks whether a stamp is valid
+     - parameter stamp: stamp to check e.g. 1:16:040922:foo::+ArSrtKd:164b3
+     - parameter resource: resource to check against
+     - parameter bits: minimum bit value to check
+     - parameter expiration: number of seconds old the stamp may be
+     - returns: true if stamp is valid
+     */
+    public func check(stamp: String,
+                      resource: String? = nil,
+                      bits: UInt,
+                      expiration: UInt? = nil) -> Bool {
+        
+        guard let stamped = Stamp(stamp: stamp) else {
+            print("Invalid stamp format")
+            return false
+        }
+        
+        if let res = resource, res != stamped.resource {
+            print("Resources do not match")
+            return false
+        }
+        
+        var count = bits
+        if let claim = stamped.claim {
+            if bits > claim {
+                return false
+            } else {
+                count = claim
+            }
+        }
+        
+        if let expiration = expiration {
+            let goodUntilDate = Date(timeIntervalSinceNow: -TimeInterval(expiration))
+            if (stamped.date < goodUntilDate) {
+                print("Stamp expired")
+                return false
+            }
+        }
+        
+        guard let digest = stamp.sha1 else {
+            return false
+        }
+        
+        let hexDigits = Int(ceil((Double(count) / 4)))
+        return digest.hasPrefix(String(repeating: "0", count: hexDigits))
+    }
+    
+    /**
+     Generates random string of chosen length
+     - parameter length:    length of random string
+     - returns: random string
+     */
+    internal func salt(length: UInt) -> String {
+        let allowedCharacters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ+/="
+        var result = ""
+        
+        for _ in 0..<length {
+            let randomValue = arc4random_uniform(UInt32(allowedCharacters.count))
+            result += "\(allowedCharacters[allowedCharacters.index(allowedCharacters.startIndex, offsetBy: Int(randomValue))])"
+        }
+        return result
+    }
+}
+
+extension String {
+    var sha1: String? {
+        let data = Data(self.utf8)
+        var digest = [UInt8](repeating: 0, count:Int(CC_SHA1_DIGEST_LENGTH))
+        data.withUnsafeBytes {
+            _ = CC_SHA1($0.baseAddress, CC_LONG(data.count), &digest)
+        }
+        let hexBytes = digest.map { String(format: "%02x", $0) }
+        return hexBytes.joined()
+    }
+}
+

Xcodes/AppleAPI/Sources/AppleAPI/Stamp.swift

@@ -0,0 +1,101 @@
+//
+//  Stamp.swift
+//  
+//
+//  Created by Matt Kiazyk on 2023-02-23.
+//
+
+import Foundation
+
+public struct Stamp {
+
+    private static let DateFormatWithoutTime = "yyMMdd"
+    private static let DateFormatWithTime = "yyMMddHHmmss"
+
+    public let version : UInt
+    public let date : Date
+    public let resource : String
+
+    // Version 1 only
+    public var claim : UInt?
+    public var counter : String?
+    public var ext : String?
+    public var random : String?
+
+    // Version 0 only
+    public var suffix : String?
+
+    init?(stamp: String) {
+        let components = stamp.components(separatedBy: ":")
+
+        if (components.count < 1) {
+            print("No stamp components. Ensure it is separated by a `:`")
+            return nil
+        }
+
+        guard let version = UInt(components[0]) else {
+            print("Unable to parse stamp version")
+            return nil
+        }
+
+        self.version = version
+
+        if self.version > 1 {
+            print("Version > 1. Not handled")
+            return nil
+        }
+
+        if (self.version == 0 && components.count < 4) {
+            print("Not enough components for version 0")
+            return nil
+        }
+
+        if (self.version == 1 && components.count < 7) {
+            print("Not enough components for version 1")
+            return nil
+        }
+
+        if (self.version == 0) {
+            if let date = Stamp.parseDate(dateString: components[1]) {
+                self.date = date
+            } else {
+                return nil
+            }
+            self.resource = components[2]
+            self.suffix = components[3]
+        } else if (self.version == 1) {
+            if let claim =  UInt(components[1]) {
+                self.claim = claim
+            }
+            if let date = Stamp.parseDate(dateString: components[2]) {
+                self.date = date
+            } else {
+                return nil
+            }
+            self.resource = components[3]
+            self.ext = components[4]
+            self.random = components[5]
+            self.counter = components[6]
+        } else {
+            return nil
+        }
+    }
+
+    private static func parseDate(dateString: String) -> Date? {
+        let formatter = DateFormatter()
+        formatter.dateFormat = Stamp.DateFormatWithoutTime
+
+        if let date = formatter.date(from: dateString) {
+            return date
+        }
+
+        formatter.dateFormat = Stamp.DateFormatWithTime
+
+        if let date = formatter.date(from: dateString) {
+            return date
+        } else {
+            print("Unable to parse date")
+            return nil
+        }
+    }
+}

Xcodes/AppleAPI/Tests/AppleAPITests/AppleAPITests.swift

@@ -2,14 +2,23 @@ import XCTest
 @testable import AppleAPI
 
 final class AppleAPITests: XCTestCase {
-    func testExample() {
-        // This is an example of a functional test case.
-        // Use XCTAssert and related functions to verify your tests produce the correct
-        // results.
-        XCTAssertEqual(AppleAPI().text, "Hello, World!")
+    
+    func testValidHashCashMint() {
+        let bits: UInt = 10
+        let resource = "bb63edf88d2f9c39f23eb4d6f0281158"
+        let testDate = "20230224001754"
+        
+//    "1:11:20230224004345:8982e236688f6ebf588c4bd4b445c4cc::877"
+//        7395f792caf430dca2d07ae7be0c63fa
+        
+        let stamp = Hashcash().mint(resource: resource, bits: bits, date: testDate)
+        XCTAssertNotNil(stamp)
+        XCTAssertEqual(stamp, "1:10:20230224001754:bb63edf88d2f9c39f23eb4d6f0281158::866")
+        
+        print(stamp)
     }
 
     static var allTests = [
-        ("testExample", testExample),
+        ("testValidHashCashMint", testValidHashCashMint),
     ]
 }