Bifid cipher: Difference between revisions
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Decrypted: The invasion will start on the first of January 2023.
</pre>
=={{header|Kotlin}}==
<syntaxhighlight lang="kotlin">
import kotlin.math.sqrt
data class Square(private val square: String) {
private val dim: Int =
sqrt(square.length.toDouble()).toInt()
fun encode(ch: Char): Pair<Int, Int> =
square.indexOf(ch).let { idx -> Pair(idx / dim, idx.mod(dim)) }
fun decode(pair: List<Int>): Char =
square[pair[0] * dim + pair[1]]
fun decode(row: Int, col: Int): Char =
square[row * dim + col]
}
class Bifid(private val square: Square) {
fun encrypt(str: String): String {
fun expandAndScatter(str: String): IntArray {
val buffer = IntArray(str.length * 2)
str.forEachIndexed { i, ch ->
with(square.encode(ch)) {
buffer[i] = first
buffer[str.length + i] = second
}
}
return buffer
}
val buffer = expandAndScatter(str)
val characters: List<Char> = buffer.asIterable()
.windowed(size = 2, step = 2)
.map { square.decode(it) }
return String(characters.toCharArray())
}
fun decrypt(str: String): String {
fun expand(str: String): IntArray {
val buffer = IntArray(str.length * 2)
for (i in buffer.indices step 2) {
with(square.encode(str[i / 2])) {
buffer[i] = first
buffer[1 + i] = second
}
}
return buffer
}
val buffer = expand(str)
val characters = str.toCharArray()
for (i in characters.indices) {
characters[i] = square.decode(buffer[i], buffer[characters.size + i])
}
return String(characters)
}
}
fun main() {
with (Bifid(Square("ABCDEFGHIKLMNOPQRSTUVWXYZ"))) {
println("\n### ABC... 5x5")
encrypt("ATTACKATDAWN").also { println("ATTACKATDAWN -> $it") }
decrypt("DQBDAXDQPDQH").also { println("DQBDAXDQPDQH -> $it") }
}
with(Bifid(Square("BGWKZQPNDSIOAXEFCLUMTHYVR"))) {
println("\n### BGW... 5x5")
encrypt("FLEEATONCE").also { println("FLEEATONCE -> $it") }
decrypt("UAEOLWRINS").also { println("UAEOLWRINS -> $it") }
encrypt("ATTACKATDAWN").also { println("ATTACKATDAWN -> $it") }
decrypt("EYFENGIWDILA").also { println("EYFENGIWDILA -> $it") }
}
with(Bifid(Square("ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"))) {
println("\n### ABC... 6x6")
encrypt("THEINVASIONWILLSTARTONTHEFIRSTOFJANUARY").also { println("$it") }
decrypt("TBPDIPHJSPOTAIVMGPCZKNSCN09BFIHK64I7BM4").also { println("$it") }
}
}
</syntaxhighlight>
{{out}}
<pre>
### ABC... 5x5
ATTACKATDAWN -> DQBDAXDQPDQH
DQBDAXDQPDQH -> ATTACKATDAWN
### BGW... 5x5
FLEEATONCE -> UAEOLWRINS
UAEOLWRINS -> FLEEATONCE
ATTACKATDAWN -> EYFENGIWDILA
EYFENGIWDILA -> ATTACKATDAWN
### ABC... 6x6
TBPDIPHJSPOTAIVMGPCZKNSCN09BFIHK64I7BM4
THEINVASIONWILLSTARTONTHEFIRSTOFJANUARY
</pre>
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