Contents

• pgsodium
• Table of Contents
  • Installation
• Usage
• Server Key Management
• Server Key Derivation
• Key Management API
• select * from pgsodium.create_key();
• Security Roles
• Transparent Column Encryption
• select * from pgsodium.create_key();
• select EXISTS (select 1 from pgsodium.valid_key where id = 'dfc44293-fa78-4a1a-9ef9-7e600e63e101');
  • One Key Id for the Entire Column
  • One Key ID per Row
  • One Key ID per Row with Nonce Support
  • One Key ID per Row with Nonce Support and Associated Data
  • TCE and ON CONFLICT UPDATE Clauses "UPSERT" Pattern
  • Postgres 15 and "Security Invoker" Views
  • Inspecting Security Labels
  • Disabling View and Trigger generation
• Simple public key encryption with crypto_box()
• Avoid secret logging
• API Reference
  • Generating Random Data
  • Secret key cryptography
    • Authenticated encryption
    • Authentication
  • Public key cryptography
    • Authenticated encryption
    • Public key signatures
    • Sealed boxes
  • Hashing
  • Password hashing
  • Key Derivation
  • Key Exchange
  • HMAC512/256
  • Advanced Stream API (XChaCha20)
  • XChaCha20-SIV
  • SignCryption

pgsodium

pgsodium is an encryption library extension for PostgreSQL using the libsodium 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 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 which can automatically encrypt and decrypt one or more columns of data in a table.

Table of Contents

• pgsodium
  • Installation
• Usage
• Server Key Management
• Server Key Derivation
• Key Management API
• Security Roles
• Transparent Column Encryption
• Simple public key encryption with crypto_box()
• Avoid secret logging
• API Reference
  • Generating Random Data
  • Secret key cryptography
    • Authenticated encryption
    • Authentication
  • Public key cryptography
    • Authenticated encryption
    • Public key signatures
    • Sealed boxes
  • Hashing
  • Password hashing
  • Key Derivation
  • Key Exchange
  • HMAC512
  • Advanced Stream API
  • XChaCha20-SIV
  • 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. You can also install pgsodium through the pgxn extension network with pgxn install pgsodium.

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.

As of version 3.0.0 pgsodium requires PostgreSQL 14+. Use pgsodium 2.0.* for earlier versions of Postgres. Once you have the extension correctly compiled you can install it into your database using the SQL:

CREATE EXTENSION pgsodium;

Note that pgsodium is very careful about the risk of search_path hacking and must go into a database schema named pgsodium. The above command will automatically create that schema. You are encouraged to always reference pgsodium functions by their fully qualified names, or by making sure that the pgsodium schema is first in your search_path.

Usage

Without using the optional Server Managed Keys feature pgsodium is a simple and straightforward interface to the libsodium API.

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() 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 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 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.

• Google Cloud's Cloud Key Management.

• Doppler SecretOps Platform.

• Zymbit Zymkey 4i Hardware Security Module.

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 process hardening 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.

You can specify the location of the get key script with a database configuration variable in either postgresql.conf or using ALTER SYSTEM:

pgsodium.getkey_script = 'path_to_script'

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. 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 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() 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 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 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();

-[ 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 |

```

pgsodium.create_key() takes the following arguments, all of them are optional:

• key_type pgsodium.key_type = 'aead-det': The type of key to create.If you do not specify a raw_key argument, a new derived key_id of the correct type will be automatically generated in key_context argument context. Possible values are:
  • aead-det
  • aead-ietf
  • hmacsha512
  • hmacsha256
  • auth
  • shorthash
  • generichash
  • kdf
  • generichash
  • kdf
  • secretbox
  • secretstream
• name text = null: The optional unique name of the key.
• raw_key bytea = null: A raw key to store encrypted, if not specified, the raw key is derived from key_id and key_context.
• raw_key_nonce bytea = null: The nonce used to encrypt the raw key with, if not specified a new random nonce will be generated.
• key_context bytea = 'pgsodium': The libsodium context to use for derivation if key_id is not null.
• parent_key uuid = null: The parent key use to encrypt the raw key. If not specified, a new unnamed key is created.
• expires timestamptz = null: The expiration time checked by the pgsodium.valid_key view.
• associated_data text = '': Extra user data you can associate with the encrypted raw key. This data is appended to the key UUID, and mixed into the encryption signature and can be authenticated with it.

Keys of the type aead-det can be used for 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 two nested layers of security roles:

• pgsodium_keyiduser Is the less privileged role that can only access keys by their UUID. This is the role you would typically give to a user facing application.

• pgsodium_keymaker is the more privileged role and can work with raw bytea And managed server keys. You would not typically give this role to a user facing application.

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.

In order to use TCE you must use keys created from the 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();

-[ 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 | associated_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; ```

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 nonce'; ```

One Key ID per Row with Nonce Support and Associated Data

The aead-det algorithm can mix user provided data into the authentication signature for the encrypted secret. This "authenticates" the plaintext and ensures that it has not been altered (or the decryption will fail). This is useful for associated useful metadata with your secrets:

```sql CREATE TABLE private.users ( id bigserial primary key, secret text, key_id uuid not null, nonce bytea, associated_data text );

SECURITY LABEL FOR pgsodium ON COLUMN private.users.secret IS 'ENCRYPT WITH KEY COLUMN key_id NONCE nonce ASSOCIATED (id, associated_data)'; ```

You can specify multiple columns as shown above with both the id and associated data column. Columns used for associated data must be deterministicly castable to text.

TCE and ON CONFLICT UPDATE Clauses "UPSERT" Pattern

UPSERT is not a command in PostgreSQL, it is one pattern among many possible when using the INSERT ... ON CONFLICT DO ... clause in Postgres to either insert a value, or do some other action, which is commonly to update the alreadt extant row that the command was attempting to INSERT. This pattern usually looks like:

sql INSERT INTO my_table (my_columns...) VALUES (new_values...) ON CONFLICT (some_unique_key_like_id) DO UPDATE SET my_data = EXCLUDED.my_data;

The statement tries to insert a row, and if there is a unique constraint violation, it will instead update the row with the value of the row that was about to be inserted.

Unfortunately, the value of the row that was about to be inserted is already encrypted, so this pattern does not work, instead to do an "UPSERT" you must combine the unencrypted data from the view with the encryted data in the table, so that the unencrypted value is "reencrypted" correctly and not "double encrypted".

The function below shows how this query can be formatted as a stored procedure, if you are using PostgREST, this is the "RPC" function to use to do the intended upsert behavior:

sql CREATE OR REPLACE FUNCTION upsert_test(p_id bigint, p_name text DEFAULT NULL, p_secret text DEFAULT NULL) RETURNS test LANGUAGE sql AS $$ INSERT INTO test (id, name, secret) VALUES (p_id, p_name, p_secret) ON CONFLICT (id) DO UPDATE SET name = coalesce(p_name, (SELECT name FROM test WHERE id = p_id)), secret = coalesce(p_secret, (SELECT decrypted_secret FROM decrypted_test WHERE id = p_id)) RETURNING * $$;

If you do not need the stored procedure you can modify the inner query to suite your specific needs as a literal SQL query.

Postgres 15 and "Security Invoker" Views

Postgres 15 added a new propery to views called security_invoker which changes the behavior of views that access an underlying table with row security labels. Before pg15, all views ran as the owner of the view itself, making interaction with RLS clumsy, starting with pg15, views that are marked as security_invoker will "run" with the privileges of the invoking user, not the owner of the view, this makes working with RLS policies simpler.

Any TCE security label can be appended with the string SECURITY INVOKER' which will cause the automatically generated view to be markedsecurity_invoker=true`. Note that you are still responsible for understanding the grants/revokes to your view and table, which can vary depending on the specific needs of your application's security model.

Inspecting Security Labels

The system catalog pg_seclabel can be hard to decipher, requiring joins to figure out which labels apply to which columns. The pgsodium.seclabel view simplifies this task by resolving the table and column names for you:

postgres=> select * from pgsodium.seclabel ; -[ RECORD 1 ]--------------------------------------------------------------------------------------------------------- nspname | tce-example relname | test2 attname | secret2 label | ENCRYPT WITH KEY COLUMN secret2_key_id ASSOCIATED (id, associated2) NONCE nonce2 -[ RECORD 2 ]--------------------------------------------------------------------------------------------------------- nspname | tce-example relname | test2 attname | secret label | ENCRYPT WITH KEY ID f8db208c-8201-466a-98cd-b0d91f5326ca ASSOCIATED (associated) NONCE nonce -[ RECORD 3 ]--------------------------------------------------------------------------------------------------------- nspname | tce-example relname | test attname | secret label | ENCRYPT WITH KEY ID 2a5500f3-9378-4134-89db-5fd870a5ce7a -[ RECORD 4 ]--------------------------------------------------------------------------------------------------------- nspname | pgsodium relname | key attname | raw_key label | ENCRYPT WITH KEY COLUMN parent_key ASSOCIATED (id, associated_data) NONCE raw_key_nonce -[ RECORD 5 ]--------------------------------------------------------------------------------------------------------- nspname | tce-example relname | bob-testt attname | secret2-test label | ENCRYPT WITH KEY COLUMN secret2_key_id-test ASSOCIATED (associated2-test) NONCE nonce2-test SECURITY INVOKER

Disabling View and Trigger generation

If you wish to disable the EVENT TRIGGER that fires and generates the trigger and view, you can turn if off with a configuration setting:

sql SET pgsodium.enable_event_trigger = 'off';

This parameter can be set in the postgresql.conf file, or passed to the server on startup with -C. Disabling trigger generation can be useful for doing migrations when you don't want trigger generation to get in the way of copying DDL from one system to another. See the postgres docs for Setting Parameters.

Simple public key encryption with crypto_box()

Here's an example usage from the test.sql that uses command-line psql 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. 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 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. Refer to those documents for details on algorithms and other libsodium specific details.

The libsodium documentation is Copyright (c) 2014-2018, Frank Denis github@pureftpd.org and released under The ISC 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

Secret key cryptography

C API Documentation

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

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 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

Public key cryptography

C API Documentation

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

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

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

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

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

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

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

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

Advanced Stream API (XChaCha20)

The stream API is for advanced users only and only provide low level encryption without authentication.

C API Documentation

XChaCha20-SIV

Deterministic/nonce-reuse resistant authenticated encryption scheme using XChaCha20.

C API Documentation

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 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