54 lines
1.2 KiB
Kotlin
54 lines
1.2 KiB
Kotlin
package com.infendro.random
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import com.infendro.bytearray.addAll
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import com.infendro.hash.HashFunction
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class HMAC internal constructor(
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private val function: HashFunction,
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) : PRNG() {
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private val random = Default
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private val hmac = com.infendro.mac.HMAC(function)
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private lateinit var K: ByteArray
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private lateinit var V: ByteArray
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init {
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val bytes = random.nextBytes(function.bytes)
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seed(bytes)
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}
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override fun seed(
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seed: ByteArray,
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) {
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K = ByteArray(function.bytes) { 0x00 }
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V = ByteArray(function.bytes) { 0x01 }
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reseed(seed)
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}
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override fun reseed(
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entropy: ByteArray,
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) {
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K = hmac.hash(K, V + byteArrayOf(0x00) + entropy)
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V = hmac.hash(K, V)
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K = hmac.hash(K, V + byteArrayOf(0x01) + entropy)
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V = hmac.hash(K, V)
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}
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override fun generate(
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count: Int,
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): ByteArray {
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val bytes = buildList {
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while (size < count) {
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V = hmac.hash(K, V)
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addAll(V)
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}
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}
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K = hmac.hash(K, V + byteArrayOf(0x00))
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V = hmac.hash(K, V)
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return bytes
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.take(count)
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.toByteArray()
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}
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}
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