49 lines
1.2 KiB
Kotlin
49 lines
1.2 KiB
Kotlin
package com.infendro.random.csprng
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import com.infendro.hash.HashFunction
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import kotlin.math.min
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import kotlin.properties.Delegates.notNull
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class HMAC internal constructor(
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private val function: HashFunction,
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) : CSPRNG() {
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private val hmac = com.infendro.mac.HMAC(function)
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private var k: UByteArray by notNull()
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private var v: UByteArray by notNull()
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override fun seed(
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seed: UByteArray,
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) {
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k = UByteArray(function.bytes) { 0x00U }
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v = UByteArray(function.bytes) { 0x01U }
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reseed(seed)
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}
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override fun reseed(
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entropy: UByteArray,
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) {
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k = hmac.hash(k, v + ubyteArrayOf(0x00U) + entropy)
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v = hmac.hash(k, v)
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k = hmac.hash(k, v + ubyteArrayOf(0x01U) + 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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): UByteArray {
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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.take(min(count - size, function.bytes)))
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}
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}.toUByteArray()
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k = hmac.hash(k, v + ubyteArrayOf(0x00U))
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v = hmac.hash(k, v)
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return bytes
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}
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}
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