[crypto.random]

This slot create a bunch of random characters, or bytes for you. The slot can optionally take a [min] and [max] argument, which defines the min/max length of the random bytes/characters returned. If not supplied, the default values for these arguments are respectively 10 and 20. This slot is useful for creating random secrets, and similar types of random strings, where you need cryptographically secured random strings. An example of generating a cryptographically secure random string of text, between 50 and 100 characters in lenght, can be found below.

Notice, the [crypto.random] slot will only return characters from a-z, A-Z and 0-9. Which makes it easily traversed using any string library. However, you can provide a [raw] argument, and set its value to boolean true, at which point the slot will return the raw bytes as a byte[]. This has a much larger amount of entropy than simply using alphanumeric characters for the same size - Which is important as you start creating keys for AES encryption, etc.

[crypto.hash] and [crypto.hash.xxx]

The [crypto.hash] slot can be used to generate hash values. When you invoke it, you can choose between having the hash returned as raw a byte[], as a "fingerprint" or as its bit encoded hex version. Below is an example of all three of these formats.

To override the hashing algorithm used when creating hash values, apply an [algorithm] argument, and set its value to the hashing algorithm you want to use. You can choose between the following hashing algorithms as you consume the above slot.

• SHA1
• MD5
• SHA256
• SHA384
• SHA512

Notice - SHA1 and MD5 is supported only for legacy reasons, and should not be used unless you have a legacy system depending upon it. Sha1 and MD5 are considered weak today. This slot also contains convenience overloads with the hashing algorithm being a part of the name of the invocation, such as illustrated below.

• [crypto.hash.sha1]
• [crypto.hash.md5]
• [crypto.hash.sha256]
• [crypto.hash.sha384]
• [crypto.hash.sha512]

In addition you canhash a file directly, without having to load it first, by providing a [filename] argument to it, such as illustrated below.

[crypto.seed]

No cryptography operation is more secure than the CSRNG instance used to generate random numbers and characters. This project accommodates for that, by explicitly allowing you to add to its CSRNG seed with something resembling the following.

Internally this is used in Magic by invoking the above slot with the value of its auth secret during startup and setup. Since this value can be manually edited by the end user, this provides you with a "super paranoid" solution to ensure extremely large amounts of entropy in its internal CSRNG instance. If you wish to further seed the CSRNG, you can invoke at any point in time, with some random humanly provided gibberish, further adding to its entropy, which later will be used when ever some cryptographically secured random strings or bytes are required, such as when generating key pairs, using combination cryptography, etc.

Cryptography

This library also supports several cryptographic services, but first a bit of cryptography theory. Public key cryptography, or what's often referred to as "asymmetric cryptography" is based upon a key pair. One of your keys are intended for being publicly shared, and is often referred to as "your public key". This key can do two important things.

1. Your public key can encrypt data such that only its private counterpart key can decrypt the data
2. Your public key can verify that a message originated from a party that has access to its private counterpart

Hence, keeping your private key as private, is of outmost importance, otherwise 3rd parties might read messages others send to you, and also impersonate you in front of others. In addition, securely delivering your public key to the other party, is of equal importance, to make sure they're using the correct public key in their communication with you. If you can keep your private key private, and securely deliver your public key to others, you have a 100% secure channel to use for communication, preventing malicious individuals from both reading what others send to you, and also tampering with the content you send to others, before the other party receives it. Hence, cryptography is about two main subjects.

1. Encrypting messages sent to you
2. Allowing you to provide guarantees that a message originated from you

Depending upon your paranoia level, you might just send your public key in an email, which is considered insecure - Or you might need to physically meet the person whom you want to communicate with, and give him a USB stick with your public key, which is considered full paranoia level. The latter might be important if you fear what's often referred to as a "man in the middle attack", where some malicious adversary, takes your public key, and gives a bogus and fake public key to the other party. This results in that the man in the middle can intercept your communication, decrypt it, and re-encrypt it with your public key, before he or she sends it to you - In addition to that he can use a similar mechanism to impersonate your signatures, allowing the other party to falsely believe some message originated from you, when it did indeed originate from a malicious "man in the middle".

There are several different ways to create a key pair, just have the above in mind as you start using cryptography in your Hyperlambda applications. Most of the cryptography functions in this library is using Bouncy Castle, which is a thoroughly tested library for doing cryptography. Bouncy Castle is owned by a charitable organisation in Australia, so they don't need to obey by American laws, reducing American intelligence services ability to coerce them to build backdoors and similar constructs into their code. Bouncy Castle is also Open Source, allowing others to scrutinise their code for such backdoors. However, with cryptography, there are no guarantees, only a "general feeling and concent" amongst developers that it's secure.

The asymmetric parts of this project is built upon RSA for its public and private key pairs.

Creating an RSA keypair

To create an RSA keypair that you can use for other cryptographic services later, you can use something as follows.

The above will return 4 nodes to you as you invoke it.

• [private] - Base64 encoded private key in DER format
• [public] - Base 64 encoded public key in DER format
• [fingerprint] - Fingerprint encoded SHA256 hash of your public key
• [fingerprint-raw] - Raw SHA256 hash of your public key

Both the [strength] and [seed] is optional above. Strength will default to 2048, which might be too weak for serious cryptography, but increasing your strength too much, might result in that the above function spends several seconds, possibly minutes to return if you set it too high - In addition to that your key pair becomes very large. The [seed] is optional, and even if you don't provide a seed argument, the default seed should still be strong enough to avoid predictions. Depending upon your paranoia level, you might want to manually seed the above slot by having users type in random text as they generate keys. A major security concern in cryptography is CSRNG, or what's referred to as "Cryptographically Secure Random Number Generators", which aren't always as cryptographically secure as we might think, since if its seeds are predictable, the random bytes it generates can easily be "replayed".

A good strength for an RSA key, is considered to be 4096, which developers around the world feels are secure enough to avoid brute force "guessing" of your private key. According to what we know about cryptography, all other concerns set aside, a 4096 bit strength key pair, should be impossible to break. If you're just playing around with cryptography to learn, 1024 is probably more than enough.

Notice, if you want the key back as raw bytes, you can supply a [raw] argument, and set its value to boolean true, at which point the returned key(s) will only be DER encoded, and returned as a raw byte[]. This might be useful, if you for instance need to persist the key to disc, as a binary file, etc. All the RSA slots can return their results as byte[] values, if you provide a [raw] argument to them, and set its value to true. If you don't provide a raw argument, the returned value will be base64 encoded DER format.

This slot will also return the fingerprint of your public key, which is useful to keep around somewhere, since it's used in other cryptographic operations to identify keys used in operation, etc. The public key's fingerprint is usually used to identify a specific key somehow.

Cryptographically signing and verifying the signature of a message

You can use a previously created private RSA key to cryptographically sign some data or message, intended to be passed over an insecure context, allowing the caller to use your public key to verify the message was in fact created by the owner of the private key. To sign some arbitrary content using your private key, and also verify the message was correctly signed with a specific key, you can use something as follows.

If somebody tampers with the content between the signing process and the verify process, an exception will be thrown during the verify stage. Something you can verify yourself by uncommenting the above [set-value] invocation. Throwing an exception is a conscious choice, due to the potential security breaches an error in your code might have, creating a false positive if you erronously invert an [if] statement. Even though this is technically "using exceptions for control flow", it has been a conscious design choice as the library was created, to avoid false positives during the verification process of a signature.

Notice, if you want the signature back as raw bytes, you can supply a [raw] argument, and set its value to boolean true, at which point the returned signature will be returned as a raw byte[]. This might be useful, if you for instance need to persist the signature to disc, as a binary file, etc. If you don't provide a raw argument, the returned value will be a base64 encoded byte array.

Encrypting and decrypting a message

To encrypt a message, you can use something as follows.

Notice how the encryption above is using the public key, and the decryption is using the private key. The encrypt slot will internally base64 encode the encrypted data for simplicity reasons, allowing you to immediately inspect it as text, since encryption will result in a byte array, which is often inconvenient to handle. You can override this by passing in a [raw] argument, and set its value to true, at which point a byte[] will be returned.

You can also supply [raw] as you invoke [crypto.rsa.decrypt] if you know the content in the message is not a string, but rather an array of byte[]. Base64 encoding a byte array normally makes it larger in size, and also require CPU resources in both ends of the communication, implying it is sometimes important to have the raw byte array, instead of its base64 encoded equivalent.

Symmetric cryptography

RSA is asymmetric cryptography, implying a different key is used for decrypting the data, than that which was used to encrypt the data. This project also supports symmetric cryptography, more specifically the AES encryption algorithm. This algorithm requires the same key to decrypt some content that was used to encrypt the data, and the key must either be 128, 192 or 256 bits long. Below is an example.

The length of the key argument you provide, becomes the bit strength of the encryption, ranging from 128 through 192 to 256 bits. However, even though the key you normally use for encrypting and decrypting when using AES is supposed to be a byte[], this project will automatically convert any passphrase specified from a string to a SHA256 hash value. This allows you to use any passphrase you wish, while avoiding reducing entropy, making it harder to crack the encrypted message.

Even though AES has low bit strength, it's still considered one of the strongest forms of cryptography that exists, assuming you use it correctly. For the record, this library does not use the built in AES library from .Net, which has several security issues, due to the way it handles padding, among other things - Neither does this library simply convert strings to byte[] arrays using Encoding.UTF.GetBytes, which significantly reduces entropy, and makes your message easily cracked by a malicious agent with some resources. Instead Magic uses Bouncy Castle, which does not have these security holes, in addition to that it creates a SHA256 hash of passphrases used, if you provide a string, keeping as much entropy as possible. However, if you want to decrypt it using other libraries, you'll have to inform the other party of that the passphrase supplied is actually supposed to be hashed using SHA256 before supplied as the key during decryption.

The library also supports using raw byte[] values as its [password] value, allowing you to generate a random array of bytes, either 16, 24 or 32 bytes in size, and use this as your passphrase directly - At which point the byte array will be used as is, and not hashed in any ways before encryption/decryption occurs.

Due to AES' blistering speed and strength, it is often wise to combine asymmetric cryptography with symmetric cryptography, which can be used by generating a random symmetric key/passphrase, then encrypt this passphrase using asymmetric cryptography, such as for instance RSA, for then to use the passphrase to encrypt the actual main data the caller wants to transmit. This has several advantages, such as reducing the size of the data sent, while still providing the benefits from asymmetric cryptography, such as securely sharing the public key, etc. Of course, sharing a symmetric key without major hassle, and/or making adversaries also get a hold of it, is practically very difficult for obvious reasons, unless you can asymmetrically encrypt the symmetric key.

If you only need a random array of 32 bytes, to use as your passphrase, in combination with for instance RSA asymmetric cryptography - You can use the [crypto.random] slot as follows.

Combining RSA and AES cryptography

AES and RSA are more useful when combined together. Hence, this project contains the following convenience slots, that combines these two cryptography functions together.

• [crypto.encrypt] - Encrypts some message using AES + RSA, and signs the message in the process
• [crypto.decrypt] - Decrypts some message using AES + RSA, optionally verifying a signature in the process
• [crypto.sign] - Cryptographically signs a message using RSA and creates a package containing both signature, signing key's fingerprint, and the content that was signed
• [crypto.verify] - The opposite of the above, that verifies the integrity of a package created with [crypto.sign]
• [crypto.get-key] - Returns the fingerprint of the RSA key that was used to encrypt some message using [crypto.encrypt] or sign some message using [crypto.sign]

The [crypto.encrypt] slot requires some message/content, a signing key, an encryption key, and your signing key's fingerprint. This slot will first cryptographically sign your message using the private key. Then it will use the public key supplied to encrypt the message, while injecting the fingerprint for the signing key and the cryptography key into the package. Below is an example.

Notice - We're using only 512 bit strength in the above example. Make sure you (at least) use 2048, preferably 4096 in real world usage. The [crypto.encrypt] slot can also optionally handle a [seed] argument, which will seed the CSRNG that's used to generate a symmetric AES encryption key.

To understand what occurs in the above Hyperlambda example, let's walk through it step by step, starting from the [crypto.encrypt] invocation.

1. The message "Some super secret message" is first cryptographically signed using the private [signing-key]
2. The signed message is then AES encrypted using a CSRNG generated random key
3. The AES key from the above is then encrypted using the [encryption-key], that's assumed to be the recipient's public key
4. The signing key's fingerprint is stored inside of the encrypted content, such that when the message is decrypted, the other party can verify that the signature originated from some trusted party
5. The encryption key's fingerprint is stored as bytes, prepended before the encrypted message, which allows the other party to retrieve the correct decryption key, according to what encryption key the caller encrypted the message with. To retrieve a cryptography operation key fingerprint, you can use [crypto.get-key]

Hence, the only thing that is in plain sight in the above encrypted message, is the fingerprint of the public key that was used to encrypt the message. Only after the message is decrypted, the signature for the message can be retrieved, together with the fingerprint of the key that was used to sign the message. Hence, what would normally be a more complete process, is that after the receiver decrypts the message, he should also verify that the signature originates from some trusted party. This can be done by simply omitting the [verify-key] argument as you invoke [crypto.decrypt], and then invoke [crypto.get-key] on the result of the decryption process, for then to use the result of [crypto.get-key] to lookup the public key used to verify the signature of the package.

Only after the message is verified, the actual content of the message is possible to read, as the value of the [crypto.verify] slot - Unless you pass in a [verify-key] during the invocation to [crypto.decrypt], at which point that key will be used to verify the signature of the message, after the package has been decrypted.

If the above invocation to [crypto.verify] does not throw an exception, we know for a fact that the message was cryptographically signed with the private key that matches its [public-key] argument. Normally the fingerprint of the sender's key is asssociated with some sort of "authorisation object" to elevate the rights of the user, only after having verified the message originated from a trusted party.

Hence, from the caller's perspective it's one invocation to encrypt and sign a message. From the receiver's perspective it's normally two steps to both decrypt and verify the integrity of a message, unless you know who the message originated from.

Notice - We're using only 512 bit strength in the above example. Make sure you (at least) use 2048, preferably 4096 in real world usage.

The encryption format

The encrypted package has the following format.

1. Signing key's fingerprint in SHA256 byte[] format, 32 bytes long
2. The length of the signature as int, 4 bytes long
3. The actual signature of the message
4. The content of the message in UTF encoded byte[] format

Afterwards the result from the above steps is encrypted using AES, with a random generated session key that is 32 bytes long. And another package is created, which is the final package, intended for being sent to the recipient. The final encryption package has a structure as follows.

1. Encryption key's fingerprint in SHA256 byte[] format, 32 bytes long
2. The length of the encrypted session key as int, 4 bytes long
3. The encrypted session key, encrypted using the recipient's public RSA key
4. The AES encrypted content from the above signing step

Hence, only when both of the above lists are done, you have a final encryption package to send to some recipient.

The other party can retrieve the encryption key used for encrypting the package, using for instance the [crypto.get-key] slot on the package. Then the receiver can use his private RSA key to decrypt the AES key, and use the decrypted AES key to decrypt the rest of the package - Which will result in getting the fingerprint of the RSA key used to sign the package, then the signature, and only then the content of the message. However, all of these steps are done automatically if you use the [crypto.decrypt] slot, except the signature verification process, unless you provide a [verify-key] argument to the decryption process.

The AES key is generated using Bouncy Castle's SecureRandom implementation, resulting in a 256 bit cryptography key. This key again is encrypted using whatever bit strength you selected as you created your RSA key pair. Hence, the message as a whole, is not stronger than whatever key strength you use as you supply a [strength] argument to the [crypto.rsa.create-key].

The above format results in that the only "meta information" an adversary can possibly pick up, is the fingerprint of the public RSA key used to encrypt the AES key, in addition to also the bit strength of this RSA key, since the bit strength of an RSA key will result in differences in the length of the encrypted AES key. An adversary will not have access to who encrypted/transmitted the package, he will not know who, if any signed the package - Or any other parts of the message - Assuming he is not able to somehow crack the AES encryption, and/or somehow retrieve the private RSA key the AES package's encryption key was encrypted with.

Blowfish password hashing

As a general security rule of thumb, passwords should never be stored in clear text, but persisted into for instance a database as "slowly hashed values with per record based salts". This prevents a whole range of security issues, such as having adversaries creating Rainbod Dictionary attacks on your passwords. This project contains two slots to implement this, and these are as follows.

• [crypto.password.hash] - Creates a password hash
• [crypto.password.verify] - Verifies a hashed password

Example usage can be found below.

The first slot invocation creates a Blowfish hash, while the second slot invocation verifies a previously created Blowfish hash, given the password as its main argument. If you exchange the second password given to [crypto.password.verify] by for instance adding one random character to it, the result will be false from the second invocation.

Internally these are the slots Magic uses when it creates its JWT authentication database, and its endpoints.

Project website

The source code for this repository can be found at github.com/polterguy/magic.lambda.crypto, and you can provide feedback, provide bug reports, etc at the same place.

Quality gates

License

This project is the copyright(c) 2020-2021 of Thomas Hansen thomas@servergardens.com, and is licensed under the terms of the LGPL version 3, as published by the Free Software Foundation. See the enclosed LICENSE file for details.

• Magic Documentation