[![Tests](https://github.com/michelp/pgsodium/actions/workflows/test.yml/badge.svg)](https://github.com/michelp/pgsodium/actions/workflows/test.yml) # pgsodium pgsodium is an encryption library extension for [PostgreSQL](https://www.postgresql.org/) using the [libsodium](https://download.libsodium.org/doc/) library for high level cryptographic algorithms. pgsodium can be used a straight interface to libsodium, but it can also use a powerful feature called [Server Key Management](#server-key-management) where pgsodium loads an external secret key into memory that is never accessible to SQL. This inaccessible root key can then be used to derive sub-keys and keypairs *by key id*. This id (type `bigint`) can then be stored *instead of the derived key*. Another advanced feature of pgsodium is [Transparent Column Encryption](#transparent-column-encryption) which can automatically encrypt and decrypt one or more columns of data in a table. # Table of Contents * [pgsodium](#pgsodium) * [Installation](#installation) * [Usage](#usage) * [Server Key Management](#server-key-management) * [Server Key Derivation](#server-key-derivation) * [Key Management API](#key-management-table) * [Security Roles](#security-roles) * [Transparent Column Encryption](#transparent-column-encryption) * [Simple public key encryption with crypto_box()](#simple-public-key-encryption-with-crypto_box) * [Avoid secret logging](#avoid-secret-logging) * [API Reference](#api-reference) * [Generating Random Data](#generating-random-data) * [Secret key cryptography](#secret-key-cryptography) * [Authenticated encryption](#authenticated-encryption) * [Authentication](#authentication) * [Public key cryptography](#public-key-cryptography) * [Authenticated encryption](#authenticated-encryption-1) * [Public key signatures](#public-key-signatures) * [Sealed boxes](#sealed-boxes) * [Hashing](#hashing) * [Password hashing](#password-hashing) * [Key Derivation](#key-derivation) * [Key Exchange](#key-exchange) * [HMAC512](#hmac512) * [Advanced Stream API](#stream) * [XChaCha20-SIV](#xchacha20-siv) * [Signcryption](#signcryption) ## Installation pgsodium requires libsodium >= 1.0.18. In addition to the libsodium library and it's development headers, you may also need the PostgreSQL header files typically in the '-dev' packages to build the extension. After installing the dependencies, clone the repo and run `sudo make install`. pgTAP tests can be run with `sudo -u postgres pg_prove test.sql` or they can be run in a self-contained Docker image. Run `./test.sh` if you have docker installed to run all tests. Note that this will run the tests against and download docker images for five different major versions of PostgreSQL (10, 11, 12, 13, 14), so it takes a while and requires a lot of network bandwidth the first time you run it. # Usage pgsodium arguments and return values for content and keys are of type `bytea`. If you wish to use `text` or `varchar` values for general content, you must make sure they are encoded correctly. The [`encode() and decode()` and `convert_to()/convert_from()`](https://www.postgresql.org/docs/12/functions-binarystring.html) binary string functions can convert from `text` to `bytea`. Simple ascii `text` strings without escape or unicode characters will be cast by the database implicitly, and this is how it is done in the tests to save time, but you should really be explicitly converting your `text` content if you wish to use pgsodium without conversion errors. Most of the libsodium API is available as SQL functions. Keys that are generated in pairs are returned as a record type, for example: ``` postgres=# SELECT * FROM crypto_box_new_keypair(); public | secret --------------------------------------------------------------------+-------------------------------------------------------------------- \xa55f5d40b814ae4a5c7e170cd6dc0493305e3872290741d3be24a1b2f508ab31 | \x4a0d2036e4829b2da172fea575a568a74a9740e86a7fc4195fe34c6dcac99976 (1 row) ``` pgsodium is careful to use memory cleanup callbacks to zero out all allocated memory used when freed. In general it is a bad idea to store secrets in the database itself, although this can be done carefully it has a higher risk. To help with this problem, pgsodium has an optional Server Key Management function that can load a hidden server key at boot that other keys are *derived* from. # Server Key Management If you add pgsodium to your [`shared_preload_libraries`](https://www.postgresql.org/docs/12/runtime-config-client.html#RUNTIME-CONFIG-CLIENT-PRELOAD) configuration and place a special script in your postgres shared extension directory, the server can preload a libsodium key on server start. **This root secret key cannot be accessed from SQL**. The only way to use the server secret key is to derive other keys from it using `derive_key()` or use the key_id variants of the API that take key ids and contexts instead of raw `bytea` keys. Server managed keys are completely optional, pgsodium can still be used without putting it in `shared_preload_libraries`, but you will need to provide your own key management. Skip ahead to the API usage section if you choose not to use server managed keys. See the file [`getkey_scripts/pgsodium_getkey_urandom.sh`](./pgsodium_getkey_urandom.sh) for an example script that returns a libsodium key using the linux `/dev/urandom` CSPRNG. pgsodium also comes with example scripts for: - [Amazon Web Service's Key Management Service](getkey_scripts/pgsodium_getkey_aws.sh). - [Google Cloud's Cloud Key Management](getkey_scripts/pgsodium_getkey_gcp.sh). - [Zymbit Zymkey 4i Hardware Security Module](getkey_scripts/pgsodium_getkey_zmk.sh). Next place `pgsodium` in your `shared_preload_libraries`. For docker containers, you can append this after the run: docker run -d ... -c 'shared_preload_libraries=pgsodium' When the server starts, it will load the secret key into memory, but this key is *never* accessible to SQL. It's possible that a sufficiently clever malicious superuser can access the key by invoking external programs, causing core dumps, looking in swap space, or other attack paths beyond the scope of pgsodium. Databases that work with encryption and keys should be extra cautious and use as many protection mitigations as possible. It is up to you to edit the get key script to get or generate the key however you want. pgsodium can be used to generate a new random key with `select encode(randombytes_buf(32), 'hex')`. Other common patterns including prompting for the key on boot, fetching it from an ssh server or managed cloud secret system, or using a command line tool to get it from a hardware security module. # Server Key Derivation New keys are derived from the primary server secret key by id and an optional context using the [libsodium Key Derivation Functions](https://doc.libsodium.org/key_derivation). Key id are just `bigint` integers. If you know the key id, key length (default 32 bytes) and the context (default 'pgsodium'), you can deterministicly generate a derived key. Derived keys can be used to encrypt data or as a seed for deterministicly generating keypairs using `crypto_sign_seed_keypair()` or `crypto_box_seed_keypair()`. It is wise not to store these secrets but only store or infer the key id, length and context. If an attacker steals your database image, they cannot generate the key even if they know the key id, length and context because they will not have the server secret key. The key id, key length and context can be secret or not, if you store them then possibly logged in database users can generate the key if they have permission to call the `derive_key()` function. Keeping the key id and/or length context secret to a client avoid this possibility and make sure to set your [database security model](https://www.postgresql.org/docs/12/sql-grant.html) correctly so that only the minimum permission possible is given to users that interact with the encryption API. Key rotation is up to you, whatever strategy you want to go from one key to the next. A simple strategy is incrementing the key id and re-encrypting from N to N+1. Newer keys will have increasing ids, you can always tell the order in which keys are superceded. A derivation context is an 8 byte `bytea`. The same key id in different contexts generate different keys. The default context is the ascii encoded bytes `pgsodium`. You are free to use any 8 byte context to scope your keys, but remember it must be a valid 8 byte `bytea` which automatically cast correctly for simple ascii string. For encoding other characters, see the [`encode() and decode()` and `convert_to()/convert_from()`](https://www.postgresql.org/docs/12/functions-binarystring.html) binary string functions. The derivable keyspace is huge given one `bigint` keyspace per context and 2^64 contexts. To derive a key: # select derive_key(1); derive_key -------------------------------------------------------------------- \x84fa0487750d27386ad6235fc0c4bf3a9aa2c3ccb0e32b405b66e69d5021247b # select derive_key(1, 64); derive_key ------------------------------------------------------------------------------------------------------------------------------------ \xc58cbe0522ac4875707722251e53c0f0cfd8e8b76b133f399e2c64c9999f01cb1216d2ccfe9448ed8c225c8ba5db9b093ff5c1beb2d1fd612a38f40e362073fb # select derive_key(1, 32, '__auth__'); derive_key -------------------------------------------------------------------- \xa9aadb2331324f399fb58576c69f51727901c651c970f3ef6cff47066ea92e95 The default keysize is `32` and the default context is `'pgsodium'`. Derived keys can be used either directly in `crypto_secretbox_*` functions for "symmetric" encryption or as seeds for generating other keypairs using for example `crypto_box_seed_new_keypair()` and `crypto_sign_seed_new_keypair()`. # select * from crypto_box_seed_new_keypair(derive_key(1)); public | secret --------------------------------------------------------------------+-------------------------------------------------------------------- \x01d0e0ec4b1fa9cc8dede88e0b43083f7e9cd33be4f91f0b25aa54d70f562278 | \x066ec431741a9d39f38c909de4a143ed39b09834ca37b6dd2ba3d015206f14ca # Key Management API pgsodium provides an API and internal table and view for simple key id and context managment. This table provides a number of useful columns including experation capability. Keys generated with this API must be used for the [Transparent Column Encryption](#transparent-column-encryption) features. Managed Keys have UUIDs for indentifiers, these UUIDs are used to lookup keys in the table. Note that the key management is based on the same [Server Key Management](#server-key-management) that uses the internal hidden root key, so both the Key Management API and Transparent Column Encryption require it. To create a new key, call the `pgsodium.create_key()` function: ``` # select * from pgsodium.create_key('This is an optional comment'); -[ RECORD 1 ]------------------------------------- id | 74d97ba2-f9e3-4a64-a032-8427cd6bd686 status | valid created | 2022-08-04 05:06:53.878502 expires | key_type | aead-det key_id | 4 key_context | \x7067736f6469756d comment | This is an optional comment user_data | ``` This key can now be used for [Transparent Column Encryption](#transparent-column-encryption). The view `pgsodium.valid_keys` filters the key table for only keys that are valid and not expired. # Security Roles The pgsodium API has three nested layers of security roles: - `pgsodium_keyiduser` Is the least privileged role, it cannot create or use raw `bytea` keys, it can only create `crypto_secretkey` nonces and access the `crypto_secretkey`, `crypto_auth` and `crypto_aead` API functions that accept key ids only. This role can also access the `randombytes` API. This is the role you would typically give to a user facing application. - `pgsodium_keyholder` Is the next more privileged layer, it can do everything `pgsodium_keyiduser` can do, but it can also use, but not create, raw `bytea` encryption keys. This role can use public key APIs like `crypto_box` and `crypto_sign`, but it cannot create keypairs. This role is useful for when keys come from external sources and must be passed as `bytea` to API functions. - `pgsodium_keymaker` is the most privileged role, it can do everything the previous roles can do, but it can also create keys, keypairs and key seeds and derive keys from key ids. Be very careful how you grant access to this role, as it can create valid secret keys derived from the root key. Note that public key apis like `crypto_box` and `crypto_sign` do not have "key id" variants, because they work with a combination of four keys, two keypairs for each of two parties. As the point of public key encryption is for each party to keep their secrets and for that secret to not be centrally derivable. You can certainly call something like `SELECT * FROM crypto_box_seed_new_keypair(derive_key(1))` and make deterministic keypairs, but then if an attacker steals your root key they can derive all keypair secrets, so this approach is not recommended. # Transparent Column Encryption pgsodium provides a useful pattern where a trigger is used to encrypt a column of data in a table which is then decrypted using a view. This is called *Transparent Column Encryption* and can be enabled with pgsodium using the [SECURITY LABEL ...]() PostgreSQL command. If an attacker acquires a dump of the table or database, they will not be able to derive the keys used to encrypt the data since they will not have the root server managed key, which is never revealed to SQL See the [example file for more details](./example/tce.sql). In order to use TCE you must use keys created from the [Key Management Table](#key-management-table) API. This API returns key ids that are UUIDs for use with the internal encryption functions used by the TCE functionality. Creating a key to use is the first step: ``` # select * from pgsodium.create_key('Optional Comment'); -[ RECORD 1 ]------------------------------------- id | dfc44293-fa78-4a1a-9ef9-7e600e63e101 status | valid created | 2022-08-03 18:50:53.355099 expires | key_type | aead-det key_id | 5 key_context | \x7067736f6469756d comment | Optional Comment user_data | ``` This key is now stored in the `pgsodium.key` table, and can be accessed via the `pgsodium.valid_key` view: ``` # select EXISTS (select 1 from pgsodium.valid_key where id = 'dfc44293-fa78-4a1a-9ef9-7e600e63e101'); -[ RECORD 1 ] exists | t ``` Now this key id can be used for simple TCE as shown in the next section. ## One Key Id for the Entire Column For the simplest case, a column can be encrypted with one key id which must be of the type `aead-det` (as created above): ```sql CREATE TABLE private.users ( id bigserial primary key, secret text); SECURITY LABEL FOR pgsodium ON COLUMN private.users.secret IS 'ENCRYPT WITH KEY ID dfc44293-fa78-4a1a-9ef9-7e600e63e101'; ``` The advantage of this approach is it is very simple, the user creates one key and labels a column with it. The cryptographic algorithm for this approach uses a *nonceless* encryption algorithm called `crypto_aead_det_xchacha20()`. If you wish to use a nonce value, see below. ## One Key ID per Row Using one key for an entire column means that whoever can decrypt one row can decrypt them all from a database dump. Also changing (rotating) the key means rewriting the whole table. A more fine grained approach is to store one key id per row: ```sql CREATE TABLE private.users ( id bigserial primary key, secret text, key_id uuid not null, nonce bytea ); SECURITY LABEL FOR pgsodium ON COLUMN private.users.secret IS 'ENCRYPT WITH KEY COLUMN key_id NONCE COLUMN nonce'; ``` This approach ensures that “cracking” the key for one row does not help decrypt any others. It also acts as a natural partition that can work in conjunction with RLS to share distinct keys between owners. ## One Key ID per Row with Nonce Support The default cryptographic algorithm for the above approach uses a *nonceless* encryption algorithm called `crypto_aead_det_xchacha20()`. This scheme has the advantage that it does not require nonce values, the disadvantage is that duplicate plaintexts will produce duplicate ciphertexts, but this information can not be used to attack the key it can only reveal the duplication. However duplication is still information, and if you want more security, slightly better performance, or you require duplicate plaintexts to have *different* ciphertexts, a unique *nonce* can be provided that mixes in some additional non-secret data that deduplicates ciphertexts for duplicate plaintext: ```sql CREATE TABLE private.users ( id bigserial primary key, secret text, key_id uuid not null, nonce bytea ); SECURITY LABEL FOR pgsodium ON COLUMN private.users.secret IS 'ENCRYPT WITH KEY COLUMN key_id NONCE COLUMN nonce'; ``` # Simple public key encryption with `crypto_box()` Here's an example usage from the test.sql that uses command-line [`psql`](https://www.postgresql.org/docs/12/app-psql.html) client commands (which begin with a backslash) to create keypairs and encrypt a message from Alice to Bob. -- Generate public and secret keypairs for bob and alice -- \gset [prefix] is a psql command that will create local -- script variables SELECT public, secret FROM crypto_box_new_keypair() \gset bob_ SELECT public, secret FROM crypto_box_new_keypair() \gset alice_ -- Create a boxnonce SELECT crypto_box_noncegen() boxnonce \gset -- Alice encrypts the box for bob using her secret key, the nonce and his public key SELECT crypto_box('bob is your uncle', :'boxnonce', :'bob_public', :'alice_secret') box \gset -- Bob decrypts the box using his secret key, the nonce, and Alice's public key SELECT crypto_box_open(:'box', :'boxnonce', :'alice_public', :'bob_secret'); Note in the above example, no secrets are *stored* in the db, but they are *interpolated* into the sql by the psql client that is sent to the server, so it's possible they can show up in the database logs. You can avoid this by using derived keys. # Avoid secret logging If you choose to work with your own keys and not restrict yourself to the `pgsodium_keyiduser` role, a useful approach is to keep keys in an external storage and disables logging while injecting the keys into local variables with [`SET LOCAL`](https://www.postgresql.org/docs/12/sql-set.html). If the images of database are hacked or stolen, the keys will not be available to the attacker. To disable logging of the key injections, `SET LOCAL` is also used to disable [`log_statements`](https://www.postgresql.org/docs/12/runtime-config-logging.html#RUNTIME-CONFIG-LOGGING-WHAT) and then re-enable normal logging afterwards. as shown below. Setting `log_statement` requires superuser privileges: -- SET LOCAL must be done in a transaction block BEGIN; -- Generate a boxnonce, and public and secret keypairs for bob and alice -- This creates secrets that are sent back to the client but not stored -- or logged. Make sure you're using an encrypted database connection! SELECT crypto_box_noncegen() boxnonce \gset SELECT public, secret FROM crypto_box_new_keypair() \gset bob_ SELECT public, secret FROM crypto_box_new_keypair() \gset alice_ -- Turn off logging and inject secrets -- into session with set local, then resume logging. SET LOCAL log_statement = 'none'; SET LOCAL app.bob_secret = :'bob_secret'; SET LOCAL app.alice_secret = :'alice_secret'; RESET log_statement; -- Now call the `current_setting()` function to get the secrets, these are not -- stored in the db but only in session memory, when the session is closed they are no longer -- accessible. -- Alice encrypts the box for bob using her secret key and his public key SELECT crypto_box('bob is your uncle', :'boxnonce', :'bob_public', current_setting('app.alice_secret')::bytea) box \gset -- Bob decrypts the box using his secret key and Alice's public key. SELECT crypto_box_open(:'box', :'boxnonce', :'alice_public', current_setting('app.bob_secret')::bytea); COMMIT; For additional paranoia you can use a function to check that the connection being used is secure or a unix domain socket. CREATE FUNCTION is_ssl_or_domain_socket() RETURNS bool LANGUAGE plpgsql AS $$ DECLARE addr text; ssl text; BEGIN SELECT inet_client_addr() INTO addr; SELECT current_setting('ssl', true) INTO ssl; IF NOT FOUND OR ((ssl IS NULL OR ssl != 'on') AND (addr IS NOT NULL OR length(addr) != 0)) THEN RETURN false; END IF; RETURN true; END; $$; This doesn't guarantee the secret won't leak out in some way of course, but it can useful if you never store secrets and send them only through secure channels back to the client, for example using the `psql` client `\gset` command shown above, or by only storing a derived key id and context. # API Reference The reference below is adapted from and uses some of the same language found at the [libsodium C API Documentation](https://doc.libsodium.org/). Refer to those documents for details on algorithms and other libsodium specific details. The libsodium documentation is Copyright (c) 2014-2018, Frank Denis and released under [The ISC License](https://github.com/jedisct1/libsodium-doc/blob/master/LICENSE). ## Generating Random Data Functions: ``` randombytes_random() -> integer randombytes_uniform(upper_bound integer) -> integer randombytes_buf(size integer) -> bytea ``` The library provides a set of functions to generate unpredictable data, suitable for creating secret keys. # select randombytes_random(); randombytes_random -------------------- 1229887405 (1 row) The `randombytes_random()` function returns an unpredictable value between 0 and 0xffffffff (included). # select randombytes_uniform(42); randombytes_uniform --------------------- 23 (1 row) The `randombytes_uniform()` function returns an unpredictable value between `0` and `upper_bound` (excluded). Unlike `randombytes_random() % upper_bound`, it guarantees a uniform distribution of the possible output values even when `upper_bound` is not a power of 2. Note that an `upper_bound < 2` leaves only a single element to be chosen, namely 0. # select randombytes_buf(42); randombytes_buf ---------------------------------------------------------------------------------------- \x27cec8d2c3de16317074b57acba2109e43b5623e1fb7cae12e8806daa21a72f058430f22ec993986fcb2 (1 row) The `randombytes_buf()` function returns a `bytea` with an unpredictable sequence of bytes. # select randombytes_new_seed() bufseed \gset # select randombytes_buf_deterministic(42, :'bufseed'); randombytes_buf_deterministic ---------------------------------------------------------------------------------------- \xa183e8d4acd68119ab2cacd9e46317ec3a00a6a8820b00339072f7c24554d496086209d7911c3744b110 (1 row) The `randombytes_buf_deterministic()` returns a `size` bytea containing bytes indistinguishable from random bytes without knowing the seed. For a given seed, this function will always output the same sequence. size can be up to 2^38 (256 GB). [C API Documentation](https://doc.libsodium.org/generating_random_data) ## Secret key cryptography [C API Documentation](https://doc.libsodium.org/secret-key_cryptography) ### Authenticated encryption Functions: ``` crypto_secretbox_keygen() -> bytea crypto_secretbox_noncegen() -> bytea crypto_secretbox(message bytea, nonce bytea, key bytea) -> bytea crypto_secretbox_open(ciphertext bytea, nonce bytea, key bytea) -> bytea ``` `crypto_secretbox_keygen()` generates a random secret key which can be used to encrypt and decrypt messages. `crypto_secretbox_noncegen()` generates a random nonce which will be used when encrypting messages. For security, each nonce must be used only once, though it is not a secret. The purpose of the nonce is to add randomness to the message so that the same message encrypted multiple times with the same key will produce different ciphertexts. `crypto_secretbox()` encrypts a message using a previously generated nonce and secret key or key id. The encrypted message can be decrypted using `crypto_secretbox_open()` Note that in order to decrypt the message, the original nonce will be needed. `crypto_secretbox_open()` decrypts a message encrypted by `crypto_secretbox()`. [C API Documentation](https://doc.libsodium.org/secret-key_cryptography/secretbox) ### Authentication Functions: ``` crypto_auth_keygen() -> bytea crypto_auth(message bytea, key bytea) -> bytea crypto_auth_verify(mac bytea, message bytea, key bytea) -> boolean ``` `crypto_auth_keygen()` generates a message-signing key for use by `crypto_auth()`. `crypto_auth()` generates an authentication tag (mac) for a combination of message and secret key. This does not encrypt the message; it simply provides a means to prove that the message has not been tampered with. To verify a message tagged in this way, use `crypto_auth_verify()`. This function is deterministic: for a given message and key, the generated mac will always be the same. Note that this requires access to the secret key, which is not something that should normally be shared. If many users need to verify message it is usually better to use [Public Key Signatures](#user-content-public-key-signatures) rather than sharing secret keys. `crypto_auth_verify()` verifies that the given mac (authentication tag) matches the supplied message and key. This tells us that the original message has not been tampered with. [C API Documentation](https://doc.libsodium.org/secret-key_cryptography/secret-key_authentication) ## Public key cryptography [C API Documentation](https://doc.libsodium.org/public-key_cryptography) ### Authenticated encryption Functions: ``` crypto_box_new_keypair() -> crypto_box_keypair crypto_box_noncegen() -> bytea crypto_box(message bytea, nonce bytea, public bytea, secret bytea) -> bytea crypto_box_open(ciphertext bytea, nonce bytea, public bytea, secret bytea) -> bytea ``` `crypto_box_new_keypair()` returns a new, randomly generated, pair of keys for public key encryption. The public key can be shared with anyone. The secret key must never be shared. `crypto_box_noncegen()` generates a random nonce which will be used when encrypting messages. For security, each nonce must be used only once, though it is not a secret. The purpose of the nonce is to add randomness to the message so that the same message encrypted multiple times with the same key will produce different ciphertexts. `crypto_box()` encrypts a message using a nonce, the intended recipient's public key and the sender's secret key. The resulting ciphertext can only be decrypted by the intended recipient using their secret key. The nonce must be sent along with the ciphertext. `crypto_box_open()` decrypts a ciphertext encrypted using `crypto_box()`. It takes the ciphertext, nonce, the sender's public key and the recipient's secret key as parameters, and returns the original message. Note that the recipient should ensure that the public key belongs to the sender. [C API Documentation](https://doc.libsodium.org/public-key_cryptography/authenticated_encryption) ### Public key signatures Functions: ``` crypto_sign_new_keypair() -> crypto_sign_keypair combined mode functions: crypto_sign(message bytea, key bytea) -> bytea crypto_sign_open(signed_message bytea, key bytea) -> bytea detached mode functions: crypto_sign_detached(message bytea, key bytea) -> bytea crypto_sign_verify_detached(sig bytea, message bytea, key bytea) -> boolean multi-part message functions: crypto_sign_init() -> bytea crypto_sign_update(state bytea, message bytea) -> bytea crypto_sign_final_create(state bytea, key bytea) -> bytea crypto_sign_final_verify(state bytea, signature bytea, key bytea) -> boolean ``` Aggregates: ``` crypto_sign_update_agg(message bytea) -> bytea crypto_sign_update_agg(state, bytea message bytea) -> bytea ``` These functions are used to authenticate that messages have have come from a specific originator (the holder of the secret key for which you have the public key), and have not been tampered with. `crypto_sign_new_keypair()` returns a new, randomly generated, pair of keys for public key signatures. The public key can be shared with anyone. The secret key must never be shared. `crypto_sign()` and `crypto_sign_verify()` operate in combined mode. In this mode the message that is being signed is combined with its signature as a single unit. `crypto_sign()` creates a signature, using the signer's secret key, which it prepends to the message. The result can be authenticated using `crypto_sign_open()`. `crypto_sign_open()` takes a signed message created by `crypto_sign()`, checks its validity using the sender's public key and returns the original message if it is valid, otherwise raises a data exception. `crypto_sign_detached()` and `crypto_sign_verify_detached()` operate in detached mode. In this mode the message is kept independent from its signature. This can be useful when wishing to sign objects that have already been stored, or where multiple signatures are desired for an object. `crypto_sign_detached()` generates a signature for message using the signer's secret key. The result is a signature which exists independently of the message, which can be verified using `crypto_sign_verify_detached()`. `crypto_sign_verify_detached()` is used to verify a signature generated by `crypto_sign_detached()`. It takes the generated signature, the original message, and the signer's public key and returns true if the signature matches the message and key, and false otherwise. `crypto_sign_init()`, `crypto_sign_update()`, `crypto_sign_final_create()`, `crypto_sign_final_verify()`, and the aggregates `crypto_sign_update_agg()` handle signatures for multi-part messages. To create or verify a signature for a multi-part message `crypto_sign_init()` is used to start the process, and then each message-part is passed to `crypto_sign_update()` or `crypto_sign_update_agg()`. Finally the signature is generated using `crypto_sign_final_update()` or verified using `crypto_sign_final_verify()`. `crypto_sign_init()` creates an initial state value which will be passed to `crypto_sign_update()` or `crypto_sign_update_agg()`. `crypto_sign_update()` or `crypto_sign_update_agg()` will be used to update the state for each part of the multi-part message. `crypto_sign_update()` takes as a parameter the state returned from `crypto_sign_init()` or the preceding call to `crypto_sign_update()` or `crypto_sign_update_agg()`. `crypto_sign_update_agg()` has two variants: one takes a previous state value, allowing multiple aggregates to be processed sequentially, and one takes no state parameter, initialising the state itself. Note that the order in which the parts of a multi-part message are processed is critical. They must be processed in the same order for signing and verifying. `crypto_sign_final_update()` takes the state returned from the last call to `crypto_sign_update()` or `crypto_sign_update_agg()` and the signer's secret key and produces the final signature. This can be checked using `crypto_sign_final_verify()`. `crypto_sign_final_verify()` is used to verify a multi-part message signature created by `crypto_sign_final_update()`. It must be preceded by the same set of calls to `crypto_sign_update()` or `crypto_sign_update_agg()` (with the same message-parts, in the same order) that were used to create the signature. It takes the state returned from the last such call, along with the signature and the signer's public key and returns true if the messages, key and signature all match. To sign or verify multi-part messages in SQL, CTE (Common Table Expression) queries are particularly effective. For example to sign a message consisting of a timestamp and several message_parts: ```.sql with init as ( select crypto_sign_init() as state ), timestamp_part as ( select crypto_sign_update(i.state, m.timestamp::bytea) as state from init i cross join messages m where m.message_id = 42 ), remaining_parts as ( select crypto_sign_update(t.state, p.message_part::bytea) as state from timestamp_part t cross join ( select message_part from message_parts where message_id = 42 order by message_part_num) p ) select crypto_sign_final_create(r.state, k.secret_key) as sig from remaining_parts r cross join keys k where k.key_name = 'xyzzy'; ``` Note that storing secret keys in a table, as is done in the example above, is a bad practice unless you have effective row-level security in place. [C API Documentation](https://doc.libsodium.org/public-key_cryptography/public-key_signatures) ### Sealed boxes Sealed boxes are designed to anonymously send messages to a recipient given its public key. Only the recipient can decrypt these messages, using its private key. While the recipient can verify the integrity of the message, it cannot verify the identity of the sender. SELECT public, secret FROM crypto_box_new_keypair() \gset bob_ SELECT crypto_box_seal('bob is your uncle', :'bob_public') sealed \gset The `sealed` psql variable is now the encrypted sealed box. To unseal it, bob needs his public and secret key: SELECT is(crypto_box_seal_open(:'sealed', :'bob_public', :'bob_secret'), 'bob is your uncle', 'crypto_box_seal/open'); [C API Documentation](https://doc.libsodium.org/public-key_cryptography/sealed_boxes) ## Hashing This API computes a fixed-length fingerprint for an arbitrary long message. Sample use cases: - File integrity checking - Creating unique identifiers to index arbitrary long data The `crypto_generichash` and `crypto_shorthash` functions can be used to generate hashes. `crypto_generichash` takes an optional hash key argument which can be NULL. In this case, a message will always have the same fingerprint, similar to the MD5 or SHA-1 functions for which crypto_generichash() is a faster and more secure alternative. But a key can also be specified. A message will always have the same fingerprint for a given key, but different keys used to hash the same message are very likely to produce distinct fingerprints. In particular, the key can be used to make sure that different applications generate different fingerprints even if they process the same data. SELECT is(crypto_generichash('bob is your uncle'), '\x6c80c5f772572423c3910a9561710313e4b6e74abc0d65f577a8ac1583673657', 'crypto_generichash'); SELECT is(crypto_generichash('bob is your uncle', NULL), '\x6c80c5f772572423c3910a9561710313e4b6e74abc0d65f577a8ac1583673657', 'crypto_generichash NULL key'); SELECT is(crypto_generichash('bob is your uncle', 'super sekret key'), '\xe8e9e180d918ea9afe0bf44d1945ec356b2b6845e9a4c31acc6c02d826036e41', 'crypto_generichash with key'); Many applications and programming language implementations were recently found to be vulnerable to denial-of-service attacks when a hash function with weak security guarantees, such as Murmurhash 3, was used to construct a hash table . In order to address this, Sodium provides the crypto_shorthash() function, which outputs short but unpredictable (without knowing the secret key) values suitable for picking a list in a hash table for a given key. This function is optimized for short inputs. The output of this function is only 64 bits. Therefore, it should not be considered collision-resistant. Use cases: - Hash tables Probabilistic - data structures such as Bloom filters - Integrity checking in interactive protocols Example: SELECT is(crypto_shorthash('bob is your uncle', 'super sekret key'), '\xe080614efb824a15', 'crypto_shorthash'); [C API Documentation](https://doc.libsodium.org/hashing) ## Password hashing SELECT lives_ok($$SELECT crypto_pwhash_saltgen()$$, 'crypto_pwhash_saltgen'); SELECT is(crypto_pwhash('Correct Horse Battery Staple', '\xccfe2b51d426f88f6f8f18c24635616b'), '\x77d029a9b3035c88f186ed0f69f58386ad0bd5252851b4e89f0d7057b5081342', 'crypto_pwhash'); SELECT ok(crypto_pwhash_str_verify(crypto_pwhash_str('Correct Horse Battery Staple'), 'Correct Horse Battery Staple'), 'crypto_pwhash_str_verify'); [C API Documentation](https://doc.libsodium.org/password_hashing) ## Key Derivation Multiple secret subkeys can be derived from a single primary key. Given the primary key and a key identifier, a subkey can be deterministically computed. However, given a subkey, an attacker cannot compute the primary key nor any other subkeys. SELECT crypto_kdf_keygen() kdfkey \gset SELECT length(crypto_kdf_derive_from_key(64, 1, '__auth__', :'kdfkey')) kdfsubkeylen \gset SELECT is(:kdfsubkeylen, 64, 'kdf byte derived subkey'); SELECT length(crypto_kdf_derive_from_key(32, 1, '__auth__', :'kdfkey')) kdfsubkeylen \gset SELECT is(:kdfsubkeylen, 32, 'kdf 32 byte derived subkey'); SELECT is(crypto_kdf_derive_from_key(32, 2, '__auth__', :'kdfkey'), crypto_kdf_derive_from_key(32, 2, '__auth__', :'kdfkey'), 'kdf subkeys are deterministic.'); [C API Documentation](https://doc.libsodium.org/key_derivation) ## Key Exchange Using the key exchange API, two parties can securely compute a set of shared keys using their peer's public key and their own secret key. SELECT crypto_kx_new_seed() kxseed \gset SELECT public, secret FROM crypto_kx_seed_new_keypair(:'kxseed') \gset seed_bob_ SELECT public, secret FROM crypto_kx_seed_new_keypair(:'kxseed') \gset seed_alice_ SELECT tx, rx FROM crypto_kx_client_session_keys( :'seed_bob_public', :'seed_bob_secret', :'seed_alice_public') \gset session_bob_ SELECT tx, rx FROM crypto_kx_server_session_keys( :'seed_alice_public', :'seed_alice_secret', :'seed_bob_public') \gset session_alice_ SELECT crypto_secretbox('hello alice', :'secretboxnonce', :'session_bob_tx') bob_to_alice \gset SELECT is(crypto_secretbox_open(:'bob_to_alice', :'secretboxnonce', :'session_alice_rx'), 'hello alice', 'secretbox_open session key'); SELECT crypto_secretbox('hello bob', :'secretboxnonce', :'session_alice_tx') alice_to_bob \gset SELECT is(crypto_secretbox_open(:'alice_to_bob', :'secretboxnonce', :'session_bob_rx'), 'hello bob', 'secretbox_open session key'); [C API Documentation](https://doc.libsodium.org/key_exchange) ## HMAC512/256 [https://en.wikipedia.org/wiki/HMAC] In cryptography, an HMAC (sometimes expanded as either keyed-hash message authentication code or hash-based message authentication code) is a specific type of message authentication code (MAC) involving a cryptographic hash function and a secret cryptographic key. As with any MAC, it may be used to simultaneously verify both the data integrity and authenticity of a message. select crypto_auth_hmacsha512_keygen() hmac512key \gset select crypto_auth_hmacsha512('food', :'hmac512key') hmac512 \gset select is(crypto_auth_hmacsha512_verify(:'hmac512', 'food', :'hmac512key'), true, 'hmac512 verified'); select is(crypto_auth_hmacsha512_verify(:'hmac512', 'fo0d', :'hmac512key'), false, 'hmac512 not verified'); [C API Documentation](https://doc.libsodium.org/advanced/hmac-sha2) ## Advanced Stream API (XChaCha20) The stream API is for advanced users only and only provide low level encryption without authentication. [C API Documentation](https://doc.libsodium.org/advanced/stream_ciphers/xchacha20) ## XChaCha20-SIV Deterministic/nonce-reuse resistant authenticated encryption scheme using XChaCha20. [C API Documentation](https://github.com/jedisct1/libsodium-xchacha20-siv) ## SignCryption Traditional authenticated encryption with a shared key allows two or more parties to decrypt a ciphertext and verify that it was created by a member of the group knowing that secret key. However, [it doesn't allow verification](https://theworld.com/~dtd/sign_encrypt/sign_encrypt7.html) of who in a group originally created a message. In order to do so, authenticated encryption has to be combined with signatures. The Toorani-Beheshti signcryption scheme achieves this using a single key pair per device, with forward security and public verifiability. [C API Documentation](https://github.com/jedisct1/libsodium-signcryption)