diff --git a/Examples/SimpleTransferCrypto/main.swift b/Examples/SimpleTransferCrypto/main.swift
index 24725f61..aa4e249b 100644
--- a/Examples/SimpleTransferCrypto/main.swift
+++ b/Examples/SimpleTransferCrypto/main.swift
@@ -14,6 +14,6 @@ public func clientFromEnvironment() -> Client {
 let client = clientFromEnvironment()
     .setMaxTransactionFee(100_000_000)
 
-try! client.transferCryptoTo(recipient: AccountId("0.0.2")!, amount: 10000)
+_ = try! client.transferCryptoTo(recipient: AccountId("0.0.2")!, amount: 10000)
 
 print("Crypto transferred successfully")
diff --git a/Package.resolved b/Package.resolved
index 7fc5470e..c57271ef 100644
--- a/Package.resolved
+++ b/Package.resolved
@@ -19,6 +19,15 @@
           "version": "0.8.0"
         }
       },
+      {
+        "package": "CryptoSwift",
+        "repositoryURL": "https://github.com/krzyzanowskim/CryptoSwift",
+        "state": {
+          "branch": null,
+          "revision": "90e5b7af823d869fa8dea5a3abc7d95b6cb04c8c",
+          "version": "1.1.3"
+        }
+      },
       {
         "package": "SwiftGRPC",
         "repositoryURL": "https://github.com/grpc/grpc-swift",
diff --git a/Package.swift b/Package.swift
index a1d72f39..465500d2 100644
--- a/Package.swift
+++ b/Package.swift
@@ -24,11 +24,12 @@ let package = Package(
         .package(url: "https://github.com/jedisct1/swift-sodium", .exact("0.8.0")),
         .package(url: "https://github.com/apple/swift-protobuf", .exact("1.6.0")),
         .package(url: "https://github.com/grpc/grpc-swift", .exact("0.9.1")),
+        .package(url: "https://github.com/krzyzanowskim/CryptoSwift", .exact("1.1.3"))
     ],
     targets: [
         .target(
             name: "Hedera",
-            dependencies: ["Sodium", "SwiftProtobuf", "SwiftGRPC"]),
+            dependencies: ["Sodium", "SwiftProtobuf", "SwiftGRPC", "CryptoSwift"]),
         .testTarget(
             name: "HederaTests",
             dependencies: ["Hedera"]),
diff --git a/Sources/Hedera/CallParams.swift b/Sources/Hedera/CallParams.swift
new file mode 100644
index 00000000..c63cf159
--- /dev/null
+++ b/Sources/Hedera/CallParams.swift
@@ -0,0 +1,140 @@
+import CryptoSwift
+
+public final class CallParams {
+    private let functionSelector: FunctionSelector?
+    private var args: [Argument]
+
+    public init(funcSelector: FunctionSelector?) {
+        self.functionSelector = funcSelector
+        args = []
+    }
+
+    private func addParamType(paramType: String) {
+        _ = try! functionSelector?.addParamType(typeName: paramType)
+    }
+
+    public func addString(param: String) -> CallParams {
+        addParamType(paramType: "string")
+        args.append(Argument(value: encodeString(param)))
+
+        return self
+    }
+
+    public final class FunctionSelector {
+        private var state: SelectorState
+        private var needsComma: Bool
+
+        private enum SelectorState {
+            case unfinished([UInt8])
+            case finished([UInt8])
+        }
+    
+        public init(_ funcName: String) {
+            needsComma = false
+            // 0x28 = '('
+            state = .unfinished(Array<UInt8>(funcName.utf8) + [0x28])
+        }
+    
+        public func addParamType(typeName: String) throws -> FunctionSelector {
+            guard case var .unfinished(bytes) = state else { 
+                throw HederaError(message: "Can't add type params to FunctionSelectors once they have finished") 
+            }
+
+            bytes += (needsComma ? [0x23] : []) + Array<UInt8>(typeName.utf8)
+
+            state = .unfinished(bytes)
+            needsComma = true
+
+            return self
+        }
+    
+        public func finishIntermediate() -> [UInt8] {
+            switch state {
+                case let .unfinished(bytes):
+                    // 0x29 = ')'
+                    return Digest.sha3(bytes + [0x29], variant: .keccak256)
+
+                case let .finished(hash):
+                    return hash
+            }
+        }
+    
+        public func finish() -> [UInt8] {
+            let hash = finishIntermediate()
+            state = .finished(hash)
+
+            return hash
+        }
+    }
+}
+
+fileprivate final class Argument {
+    private let value: [UInt8]
+    private let isDynamic: Bool
+
+    // this is a different init function so that it avoids the throws annotation
+    init(value: [UInt8]) {
+        self.value = value
+        self.isDynamic = true
+
+    }
+
+    init(value: [UInt8], isDynamic: Bool) throws {
+        guard isDynamic || value.count == 32 else {
+            throw HederaError(message: "invalid argument: value argument that was not 32 bytes") 
+        }
+
+        self.value = value
+        self.isDynamic = isDynamic
+    }
+}
+
+private func encodeString(_ param: String) -> [UInt8] {
+    let strBytes = Array<UInt8>(param.utf8)
+
+    // prepend the size of the string.
+    return int256(val: Int64(strBytes.count), bitwidth: 32) + padRight(strBytes)
+}
+
+private func encodeBytes(bytes: [UInt8]) -> [UInt8] {
+    return int256(val: Int64(bytes.count), bitwidth: 32) + padRight(bytes)
+}
+
+private func encodeArray(elements: [[UInt8]], prependLen: Bool) -> [UInt8] {
+    if (prependLen) {
+        return int256(val: Int64(elements.count), bitwidth: 32) + elements.joined()
+    } else {
+        return Array(elements.joined())
+    }
+}
+
+private func int256(val: Int64, bitwidth: UInt8) -> [UInt8] {
+    // this uses int internally for convinence, 
+    // but uses UInt8 as a param type to ensure
+    //  that nothing tries to use a bitwidth too big.
+    let bytes = Int(min(bitwidth, 64) / 8)
+    let remainder = rem(bytes) 
+    var output = Array<UInt8>(repeating: val < 0 ? 0xff : 0x00, count: bytes + remainder)
+
+    for i in stride(from: bytes - 1, through: 0, by: -1) {
+        output[remainder + i] = UInt8(val >> (i * 8))
+    }
+
+    return output
+}
+
+private func padLeft(_ bytes: [UInt8], signExtend: Bool = false) -> [UInt8] {
+    return Array<UInt8>(repeating: signExtend ? 0xff : 0x00, count: rem(bytes.count)) + bytes
+}
+
+private func padRight(_ bytes: [UInt8]) -> [UInt8] {
+    return bytes + Array<UInt8>(repeating: 0x00, count: rem(bytes.count))
+}
+
+private func rem(_ val: Int) -> Int {
+    guard val % 32 == 0 else {
+        return 0
+    }
+
+    return 32 - val % 32
+}
\ No newline at end of file