multiplatform-crypto contains pure kotlin implementations, is not reviewed, should be considered unsafe and only for prototyping or experimentation purposes.
multiplatform-crypto-delegated relies on platform specific implementations, like libsodium, but care should still be taken that the kotlin code is not reviewed or proven safe.

Notes & Roadmap

The API will move fast and break often until v1.0

Next steps:

Expand API (AEAD, ECC ...)

Should I use this in production?

No, until it is reviewed.

Should I use this in code that is critical in any way, shape or form?

No, but even if after being warned you decide to, then use multiplatform-crypto-delegated.

Why?

This is an experimental implementation, mostly for expanding personal understanding of cryptography. It's not peer reviewed, not guaranteed to be bug free, and not guaranteed to be secure.

Currently supported

Hashing functions

Blake2b
SHA512
SHA256

Symmetric cipher

AES
- Modes: CBC, CTR

Key Derivation

Argon2

AEAD

TODO()

Delegated flavor dependancy table

The following table describes which library is used for particular cryptographic primitive

Primitive	JVM	JS	Native
Blake2b	JCE	libsodium.js	libsodium
SHA256	JCE	libsodium.js	libsodium
SHA512	JCE	libsodium.js	libsodium
AES-CBC	JCE	libsodium.js	libsodium
AES-CTR	JCE	libsodium.js	libsodium

Integration

Gradle

Kotlin

implementation("com.ionspin.kotlin:multiplatform-crypto:0.0.5")

or

implementation("com.ionspin.kotlin:multiplatform-crypto-delegated:0.0.5")

Snapshot builds

repositories {
    maven {
        url = uri("https://oss.sonatype.org/content/repositories/snapshots")
    }
}
implementation("com.ionspin.kotlin:multiplatform-crypto:0.0.6-SNAPSHOT")

Usage

Hashes

Hashes are provided in two versions, "stateless", usually the companion object of the hash, which takes the data to be hashed in one go, and "updatable" which can be fed data in chunks.

Blake2b

You can use Blake 2b in two modes

Stateless version

You need to deliver the complete data that is to be hashed in one go

val input = "abc"
val result = Blake2b.digest(input)

Result is returned as a UByteArray

Updatable instance version

You can create an instance and feed the data by using update(input : UByteArray) call. Once all data is supplied, you should call digest().

If you want to use Blake2b with a key, you should supply it when creating the Blake2b instance.

val test = "abc"
val key = "key"
val blake2b = Blake2b(key)
blake2b.update(test)
val result = blake2b.digest()

After digest is called, the instance is reset and can be reused (Keep in mind key stays the same for the particular instance).

SHA2 (SHA256 and SHA512)

Stateless version

You need to deliver the complete data that is to be hashed in one go. You can either provide the UByteArray as input or String. Result is always returned as UByteArray (At least in verision 0.0.1)

val input = "abc"
val result = Sha256.digest(input)

val input ="abc"
val result = Sha512.digest(message = input.encodeToByteArray().map { it.toUByte() }.toTypedArray())

Result is returned as a UByteArray

Updateable version

Or you can use the updatable instance version

val sha256 = Sha256()
sha256.update("abc")
val result = sha256.digest()

val sha512 = Sha512()
sha512.update("abc")
val result = sha512.digest()

Symmetric encryption

AES

Aes is available with CBC and CTR mode through AesCbc and AesCtr classes/objects. Similarly to hashes you can either use stateless or updateable version.

Initialization vector, or counter states are chosen by the SDK automaticaly, and returned alongside encrypted data

Stateless AesCbc and AesCtr

AesCtr

val keyString = "4278b840fb44aaa757c1bf04acbe1a3e"
val key = AesKey.Aes128Key(keyString)
val plainText = "6bc1bee22e409f96e93d7e117393172aae2d8a571e03ac9c9eb76fac45af8e5130c81c46a35ce411e5fbc1191a0a52eff69f2445df4f9b17ad2b417be66c3710"

val encryptedDataAndInitializationVector = AesCtr.encrypt(key, plainText.hexStringToUByteArray())
val decrypted = AesCtr.decrypt(
    key,
    encryptedDataAndInitializationVector.encryptedData,
    encryptedDataAndInitializationVector.initialCounter
)
plainText == decrypted.toHexString()

AesCbc


val keyString = "4278b840fb44aaa757c1bf04acbe1a3e"
val key = AesKey.Aes128Key(keyString)

val plainText = "3c888bbbb1a8eb9f3e9b87acaad986c466e2f7071c83083b8a557971918850e5"

val encryptedDataAndInitializationVector = AesCbc.encrypt(key, plainText.hexStringToUByteArray())
val decrypted = AesCbc.decrypt(
    key,
    encryptedDataAndInitializationVector.encryptedData,
    encryptedDataAndInitializationVector.initilizationVector
)
plainText == decrypted.toHexString()

Key derivation

Argon2

NOTE: This implementation is tested against KAT generated by reference Argon2 implementation, which does not follow specification completely. See this issue https://github.com/P-H-C/phc-winner-argon2/issues/183

val argon2Instance = Argon2(
            password = "Password",
            salt = "RandomSalt",
            parallelism = 8,
            tagLength = 64U,
            requestedMemorySize = 256U, //4GB
            numberOfIterations = 4U,
            key = "",
            associatedData = "",
            argonType = ArgonType.Argon2id
        )
val tag = argon2Instance.derive()
val tagString = tag.map { it.toString(16).padStart(2, '0') }.joinToString(separator = "")
val expectedTagString = "c255e3e94305817d5e09a7c771e574e3a81cc78fef5da4a9644b6df0" +
        "0ba1c9b424e3dd0ce7e600b1269b14c84430708186a8a60403e1bfbda935991592b9ff37"
println("Tag: ${tagString}")
assertEquals(tagString, expectedTagString)