iOS Swift算法之KDF2

后端用Java开发的，用到了org.bouncycastle.crypto.generators.KDF2BytesGenerator，一开始在网上各种搜，没找到相关的接口或第三方库，白白浪费了几天时间，后面才想到照着Java代码自己实现，于是乎参考BaseKDFBytesGenerator.java轻松搞定。

import Foundation
import CryptoKitclass KDF2BytesGenerator {static func generateBytes(shared: Array<UInt8>, iv: Array<UInt8>?) -> Array<UInt8> {var outOff = 0var len = 16let oBytes = lenlet outLen = SHA256.byteCountlet cThreshold = (oBytes + outLen - 1) / outLenlet counterStart = 1var out = Array<UInt8>(repeating: 0, count: oBytes)var C = Array<UInt8>(repeating: 0, count: 4)intToBigEndian(counterStart, &C, 0)var counterBase = counterStart & ~0xFFfor _ in 0..<cThreshold {var digest = SHA256()digest.update(data: shared)digest.update(data: C)if (iv != nil){digest.update(data: iv!)}let dig = digest.finalize().map { (e:UInt8) ine}if len > outLen {uint8ArrayCopy(dig, 0, &out, outOff, outLen)outOff += outLenlen -= outLen} else {uint8ArrayCopy(dig, 0, &out, outOff, len)}if 1 + C[3] == 0 {C[3] += 1counterBase += 0x100intToBigEndian(counterBase, &C, 0)}}return out}static func uint8ArrayCopy(_ src: Array<UInt8>, _ srcPos: Int, _ dest: UnsafeMutablePointer<UInt8>, _ destPos: Int, _ length: Int) {let end = srcPos + lengthfor i in srcPos..<end {dest[destPos + i - srcPos] = src[i]}}static func intToBigEndian(_ value: Int, _ arr: UnsafeMutablePointer<UInt8>, _ offset: Int) {arr[offset] = UInt8((value >> 24) & 0xff)arr[offset + 1] = UInt8((value >> 16) & 0xff)arr[offset + 2] = UInt8((value >> 8) & 0xff)arr[offset + 3] = UInt8(value & 0xff)}
}