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
- 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
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
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
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
hacking and must go into a database schema named
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
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
varchar values for general
content, you must make sure they are encoded correctly. The
encode() and decode() and
binary string functions can convert from
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
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
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
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
for an example script that returns a libsodium key using the linux
pgsodium also comes with example scripts for:
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
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
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_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
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
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
Derived keys can be used either directly in
functions for "symmetric" encryption or as seeds for generating other
keypairs using for example
# 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
# 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
key_type pgsodium.key_type = 'aead-det': The type of key to create.If you do not specify a
raw_keyargument, a new derived key_id of the correct type will be automatically generated in
key_contextargument context. Possible values are:
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
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_idis 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
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.
The pgsodium API has two nested layers of security roles:
pgsodium_keyiduserIs 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_keymakeris the more privileged role and can work with raw
byteaAnd managed server keys. You would not typically give this role to a user facing application.
Note that public key apis like
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
# 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):
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
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:
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
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:
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
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:
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
Simple public key encryption with
Here's an example usage from the test.sql that uses command-line
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
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
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
\gset command shown above, or by only storing a
derived key id and context.
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 firstname.lastname@example.org and released under The ISC License.
Generating Random Data
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)
randombytes_random() function returns an unpredictable value
between 0 and 0xffffffff (included).
# select randombytes_uniform(42); randombytes_uniform --------------------- 23 (1 row)
randombytes_uniform() function returns an unpredictable value
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)
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)
randombytes_buf_deterministic() returns a
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).
Secret key cryptography
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
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_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() 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.
Public key cryptography
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.
Public key signatures
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
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_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
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
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
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() is used to verify a signature
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
crypto_sign_final_verify(), and the
crypto_sign_update_agg() handle signatures for
multi-part messages. To create or verify a signature for a multi-part
crypto_sign_init() is used to start the process, and then each
message-part is passed to
crypto_sign_update_agg(). Finally the signature is generated using
crypto_sign_final_update() or verified using
crypto_sign_init() creates an initial state value which will be
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_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
crypto_sign_update_agg() and the
signer's secret key and produces the final signature. This can be
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_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:
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.
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
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');
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
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.
- Hash tables Probabilistic
- data structures such as Bloom filters
- Integrity checking in interactive protocols
SELECT is(crypto_shorthash('bob is your uncle', 'super sekret key'), '\xe080614efb824a15', 'crypto_shorthash');
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');
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.');
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');
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');
Advanced Stream API (XChaCha20)
The stream API is for advanced users only and only provide low level encryption without authentication.
Deterministic/nonce-reuse resistant authenticated encryption scheme using XChaCha20.
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.