# Encryption.nim
import nimcrypto
import nimcrypto/sysrand


var buf: array[8, byte] = [byte  0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41]

when isMainModule:
    var
        data = buf
        envkey: string = "RANDOMKEY"

        ectx, dctx: CTR[aes256]
        key: array[aes256.sizeKey, byte]
        iv: array[aes256.sizeBlock, byte]
        plaintext = newSeq[byte](len(data))
        enctext = newSeq[byte](len(data))
        dectext = newSeq[byte](len(data))

    # create random iv
    discard randomBytes(addr iv[0], 16)

    # do not need to pad data, CTR mode works byte by byte
    copyMem(addr plaintext[0], addr data[0], len(data))

    # expand key to 32 bytes using sha256 as the kdf
    var expandedKey = sha256.digest(envkey)
    copyMem(addr key[0], addr expandedKey.data[0], len(expandedKey.data))

    # create encryption context
    ectx.init(key, iv)
    ectx.encrypt(plaintext, enctext)
    ectx.clear()

    dctx.init(key, iv)
    dctx.decrypt(enctext, dectext)
    dctx.clear()

    echo "IV: ", iv
    echo "KEY: ", key
    echo "ENCRYPTED TEXT: ", enctext
    echo "DECRYPTED TEXT: ", dectext

# OUTPUT:
IV: [231, 153, 185, 13, 155, 130, 79, 45, 19, 111, 11, 28, 250, 5, 52, 252]
KEY: [246, 215, 109, 82, 228, 30, 121, 45, 105, 211, 137, 142, 245, 112, 196, 97, 55, 90, 240, 2, 53, 192, 167, 177, 149, 204, 89, 124, 45, 145, 200, 91]
ENCRYPTED TEXT: @[130, 65, 75, 33, 31, 237, 85, 32]
DECRYPTED TEXT: @[65, 65, 65, 65, 65, 65, 65, 65]

# Decryption.nim
when isMainModule:
    var data = [130, 65, 75, 33, 31, 237, 85, 32]
    var key = [246, 215, 109, 82, 228, 30, 121, 45, 105, 211, 137, 142, 245, 112, 196, 97, 55, 90, 240, 2, 53, 192, 167, 177, 149, 204, 89, 124, 45, 145, 200, 91]
    var iv = [231, 153, 185, 13, 155, 130, 79, 45, 19, 111, 11, 28, 250, 5, 52, 252]

    var
        ectx, dctx: CTR[aes256]
        enctext = newSeq[byte](len(data))
        dectext = newSeq[byte](len(data))

    # copy data to enctext
    copyMem(addr enctext[0], addr data[0], len(data))

    # convert key int array to byte array
    var keyB: array[key.len, byte]
    for i in low(key) .. high(key):
        keyB[i] = key[i].byte

    # convert iv int array to byte array
    var ivB: array[iv.len, byte]
    for i in low(iv) .. high(iv):
        ivB[i] = iv[i].byte

    ectx.init(keyB, ivB)
    ectx.clear()

    dctx.init(keyB, ivB)
    dctx.decrypt(enctext, dectext)
    dctx.clear()

    var out: array[data.len, byte]
    for i in low(dectext) .. high(dectext):
        sc[i] = dectext[i].byte

    echo out

# OUTPUT
[65, 0, 10, 96, 94, 172, 20, 97]