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><DIV
CLASS="SECT1"
><H1
CLASS="SECT1"
><A
NAME="PGCRYPTO"
>F.25. pgcrypto</A
></H1
><P
> The <TT
CLASS="FILENAME"
>pgcrypto</TT
> module provides cryptographic functions for
<SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
>.
</P
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN150185"
>F.25.1. General Hashing Functions</A
></H2
><DIV
CLASS="SECT3"
><H3
CLASS="SECT3"
><A
NAME="AEN150187"
>F.25.1.1. <CODE
CLASS="FUNCTION"
>digest()</CODE
></A
></H3
><PRE
CLASS="SYNOPSIS"
>digest(data text, type text) returns bytea
digest(data bytea, type text) returns bytea</PRE
><P
> Computes a binary hash of the given <TT
CLASS="PARAMETER"
>data</TT
>.
<TT
CLASS="PARAMETER"
>type</TT
> is the algorithm to use.
Standard algorithms are <TT
CLASS="LITERAL"
>md5</TT
>, <TT
CLASS="LITERAL"
>sha1</TT
>,
<TT
CLASS="LITERAL"
>sha224</TT
>, <TT
CLASS="LITERAL"
>sha256</TT
>,
<TT
CLASS="LITERAL"
>sha384</TT
> and <TT
CLASS="LITERAL"
>sha512</TT
>.
If <TT
CLASS="FILENAME"
>pgcrypto</TT
> was built with
OpenSSL, more algorithms are available, as detailed in
<A
HREF="pgcrypto.html#PGCRYPTO-WITH-WITHOUT-OPENSSL"
>Table F-20</A
>.
</P
><P
> If you want the digest as a hexadecimal string, use
<CODE
CLASS="FUNCTION"
>encode()</CODE
> on the result. For example:
</P><PRE
CLASS="PROGRAMLISTING"
>CREATE OR REPLACE FUNCTION sha1(bytea) returns text AS $$
SELECT encode(digest($1, 'sha1'), 'hex')
$$ LANGUAGE SQL STRICT IMMUTABLE;</PRE
><P>
</P
></DIV
><DIV
CLASS="SECT3"
><H3
CLASS="SECT3"
><A
NAME="AEN150205"
>F.25.1.2. <CODE
CLASS="FUNCTION"
>hmac()</CODE
></A
></H3
><PRE
CLASS="SYNOPSIS"
>hmac(data text, key text, type text) returns bytea
hmac(data bytea, key text, type text) returns bytea</PRE
><P
> Calculates hashed MAC for <TT
CLASS="PARAMETER"
>data</TT
> with key <TT
CLASS="PARAMETER"
>key</TT
>.
<TT
CLASS="PARAMETER"
>type</TT
> is the same as in <CODE
CLASS="FUNCTION"
>digest()</CODE
>.
</P
><P
> This is similar to <CODE
CLASS="FUNCTION"
>digest()</CODE
> but the hash can only be
recalculated knowing the key. This prevents the scenario of someone
altering data and also changing the hash to match.
</P
><P
> If the key is larger than the hash block size it will first be hashed and
the result will be used as key.
</P
></DIV
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN150217"
>F.25.2. Password Hashing Functions</A
></H2
><P
> The functions <CODE
CLASS="FUNCTION"
>crypt()</CODE
> and <CODE
CLASS="FUNCTION"
>gen_salt()</CODE
>
are specifically designed for hashing passwords.
<CODE
CLASS="FUNCTION"
>crypt()</CODE
> does the hashing and <CODE
CLASS="FUNCTION"
>gen_salt()</CODE
>
prepares algorithm parameters for it.
</P
><P
> The algorithms in <CODE
CLASS="FUNCTION"
>crypt()</CODE
> differ from usual hashing algorithms
like MD5 or SHA1 in the following respects:
</P
><P
></P
><OL
TYPE="1"
><LI
><P
> They are slow. As the amount of data is so small, this is the only
way to make brute-forcing passwords hard.
</P
></LI
><LI
><P
> They use a random value, called the <I
CLASS="FIRSTTERM"
>salt</I
>, so that users
having the same password will have different encrypted passwords.
This is also an additional defense against reversing the algorithm.
</P
></LI
><LI
><P
> They include the algorithm type in the result, so passwords hashed with
different algorithms can co-exist.
</P
></LI
><LI
><P
> Some of them are adaptive — that means when computers get
faster, you can tune the algorithm to be slower, without
introducing incompatibility with existing passwords.
</P
></LI
></OL
><P
> <A
HREF="pgcrypto.html#PGCRYPTO-CRYPT-ALGORITHMS"
>Table F-17</A
> lists the algorithms
supported by the <CODE
CLASS="FUNCTION"
>crypt()</CODE
> function.
</P
><DIV
CLASS="TABLE"
><A
NAME="PGCRYPTO-CRYPT-ALGORITHMS"
></A
><P
><B
>Table F-17. Supported Algorithms for <CODE
CLASS="FUNCTION"
>crypt()</CODE
></B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><COL><COL><COL><COL><COL><THEAD
><TR
><TH
>Algorithm</TH
><TH
>Max Password Length</TH
><TH
>Adaptive?</TH
><TH
>Salt Bits</TH
><TH
>Description</TH
></TR
></THEAD
><TBODY
><TR
><TD
><TT
CLASS="LITERAL"
>bf</TT
></TD
><TD
>72</TD
><TD
>yes</TD
><TD
>128</TD
><TD
>Blowfish-based, variant 2a</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
>md5</TT
></TD
><TD
>unlimited</TD
><TD
>no</TD
><TD
>48</TD
><TD
>MD5-based crypt</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
>xdes</TT
></TD
><TD
>8</TD
><TD
>yes</TD
><TD
>24</TD
><TD
>Extended DES</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
>des</TT
></TD
><TD
>8</TD
><TD
>no</TD
><TD
>12</TD
><TD
>Original UNIX crypt</TD
></TR
></TBODY
></TABLE
></DIV
><DIV
CLASS="SECT3"
><H3
CLASS="SECT3"
><A
NAME="AEN150279"
>F.25.2.1. <CODE
CLASS="FUNCTION"
>crypt()</CODE
></A
></H3
><PRE
CLASS="SYNOPSIS"
>crypt(password text, salt text) returns text</PRE
><P
> Calculates a crypt(3)-style hash of <TT
CLASS="PARAMETER"
>password</TT
>.
When storing a new password, you need to use
<CODE
CLASS="FUNCTION"
>gen_salt()</CODE
> to generate a new <TT
CLASS="PARAMETER"
>salt</TT
> value.
To check a password, pass the stored hash value as <TT
CLASS="PARAMETER"
>salt</TT
>,
and test whether the result matches the stored value.
</P
><P
> Example of setting a new password:
</P><PRE
CLASS="PROGRAMLISTING"
>UPDATE ... SET pswhash = crypt('new password', gen_salt('md5'));</PRE
><P>
</P
><P
> Example of authentication:
</P><PRE
CLASS="PROGRAMLISTING"
>SELECT pswhash = crypt('entered password', pswhash) FROM ... ;</PRE
><P>
This returns <TT
CLASS="LITERAL"
>true</TT
> if the entered password is correct.
</P
></DIV
><DIV
CLASS="SECT3"
><H3
CLASS="SECT3"
><A
NAME="AEN150293"
>F.25.2.2. <CODE
CLASS="FUNCTION"
>gen_salt()</CODE
></A
></H3
><PRE
CLASS="SYNOPSIS"
>gen_salt(type text [, iter_count integer ]) returns text</PRE
><P
> Generates a new random salt string for use in <CODE
CLASS="FUNCTION"
>crypt()</CODE
>.
The salt string also tells <CODE
CLASS="FUNCTION"
>crypt()</CODE
> which algorithm to use.
</P
><P
> The <TT
CLASS="PARAMETER"
>type</TT
> parameter specifies the hashing algorithm.
The accepted types are: <TT
CLASS="LITERAL"
>des</TT
>, <TT
CLASS="LITERAL"
>xdes</TT
>,
<TT
CLASS="LITERAL"
>md5</TT
> and <TT
CLASS="LITERAL"
>bf</TT
>.
</P
><P
> The <TT
CLASS="PARAMETER"
>iter_count</TT
> parameter lets the user specify the iteration
count, for algorithms that have one.
The higher the count, the more time it takes to hash
the password and therefore the more time to break it. Although with
too high a count the time to calculate a hash may be several years
— which is somewhat impractical. If the <TT
CLASS="PARAMETER"
>iter_count</TT
>
parameter is omitted, the default iteration count is used.
Allowed values for <TT
CLASS="PARAMETER"
>iter_count</TT
> depend on the algorithm and
are shown in <A
HREF="pgcrypto.html#PGCRYPTO-ICFC-TABLE"
>Table F-18</A
>.
</P
><DIV
CLASS="TABLE"
><A
NAME="PGCRYPTO-ICFC-TABLE"
></A
><P
><B
>Table F-18. Iteration Counts for <CODE
CLASS="FUNCTION"
>crypt()</CODE
></B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><COL><COL><COL><COL><THEAD
><TR
><TH
>Algorithm</TH
><TH
>Default</TH
><TH
>Min</TH
><TH
>Max</TH
></TR
></THEAD
><TBODY
><TR
><TD
><TT
CLASS="LITERAL"
>xdes</TT
></TD
><TD
>725</TD
><TD
>1</TD
><TD
>16777215</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
>bf</TT
></TD
><TD
>6</TD
><TD
>4</TD
><TD
>31</TD
></TR
></TBODY
></TABLE
></DIV
><P
> For <TT
CLASS="LITERAL"
>xdes</TT
> there is an additional limitation that the
iteration count must be an odd number.
</P
><P
> To pick an appropriate iteration count, consider that
the original DES crypt was designed to have the speed of 4 hashes per
second on the hardware of that time.
Slower than 4 hashes per second would probably dampen usability.
Faster than 100 hashes per second is probably too fast.
</P
><P
> <A
HREF="pgcrypto.html#PGCRYPTO-HASH-SPEED-TABLE"
>Table F-19</A
> gives an overview of the relative slowness
of different hashing algorithms.
The table shows how much time it would take to try all
combinations of characters in an 8-character password, assuming
that the password contains either only lower case letters, or
upper- and lower-case letters and numbers.
In the <TT
CLASS="LITERAL"
>crypt-bf</TT
> entries, the number after a slash is
the <TT
CLASS="PARAMETER"
>iter_count</TT
> parameter of
<CODE
CLASS="FUNCTION"
>gen_salt</CODE
>.
</P
><DIV
CLASS="TABLE"
><A
NAME="PGCRYPTO-HASH-SPEED-TABLE"
></A
><P
><B
>Table F-19. Hash Algorithm Speeds</B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><COL><COL><COL><COL><THEAD
><TR
><TH
>Algorithm</TH
><TH
>Hashes/sec</TH
><TH
>For <TT
CLASS="LITERAL"
>[a-z]</TT
></TH
><TH
>For <TT
CLASS="LITERAL"
>[A-Za-z0-9]</TT
></TH
></TR
></THEAD
><TBODY
><TR
><TD
><TT
CLASS="LITERAL"
>crypt-bf/8</TT
></TD
><TD
>28</TD
><TD
>246 years</TD
><TD
>251322 years</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
>crypt-bf/7</TT
></TD
><TD
>57</TD
><TD
>121 years</TD
><TD
>123457 years</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
>crypt-bf/6</TT
></TD
><TD
>112</TD
><TD
>62 years</TD
><TD
>62831 years</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
>crypt-bf/5</TT
></TD
><TD
>211</TD
><TD
>33 years</TD
><TD
>33351 years</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
>crypt-md5</TT
></TD
><TD
>2681</TD
><TD
>2.6 years</TD
><TD
>2625 years</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
>crypt-des</TT
></TD
><TD
>362837</TD
><TD
>7 days</TD
><TD
>19 years</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
>sha1</TT
></TD
><TD
>590223</TD
><TD
>4 days</TD
><TD
>12 years</TD
></TR
><TR
><TD
><TT
CLASS="LITERAL"
>md5</TT
></TD
><TD
>2345086</TD
><TD
>1 day</TD
><TD
>3 years</TD
></TR
></TBODY
></TABLE
></DIV
><P
> Notes:
</P
><P
></P
><UL
><LI
><P
> The machine used is a 1.5GHz Pentium 4.
</P
></LI
><LI
><P
> <TT
CLASS="LITERAL"
>crypt-des</TT
> and <TT
CLASS="LITERAL"
>crypt-md5</TT
> algorithm numbers are
taken from John the Ripper v1.6.38 <TT
CLASS="LITERAL"
>-test</TT
> output.
</P
></LI
><LI
><P
> <TT
CLASS="LITERAL"
>md5</TT
> numbers are from mdcrack 1.2.
</P
></LI
><LI
><P
> <TT
CLASS="LITERAL"
>sha1</TT
> numbers are from lcrack-20031130-beta.
</P
></LI
><LI
><P
> <TT
CLASS="LITERAL"
>crypt-bf</TT
> numbers are taken using a simple program that
loops over 1000 8-character passwords. That way I can show the speed
with different numbers of iterations. For reference: <TT
CLASS="LITERAL"
>john
-test</TT
> shows 213 loops/sec for <TT
CLASS="LITERAL"
>crypt-bf/5</TT
>.
(The very small
difference in results is in accordance with the fact that the
<TT
CLASS="LITERAL"
>crypt-bf</TT
> implementation in <TT
CLASS="FILENAME"
>pgcrypto</TT
>
is the same one used in John the Ripper.)
</P
></LI
></UL
><P
> Note that <SPAN
CLASS="QUOTE"
>"try all combinations"</SPAN
> is not a realistic exercise.
Usually password cracking is done with the help of dictionaries, which
contain both regular words and various mutations of them. So, even
somewhat word-like passwords could be cracked much faster than the above
numbers suggest, while a 6-character non-word-like password may escape
cracking. Or not.
</P
></DIV
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN150426"
>F.25.3. PGP Encryption Functions</A
></H2
><P
> The functions here implement the encryption part of the OpenPGP (RFC 4880)
standard. Supported are both symmetric-key and public-key encryption.
</P
><P
> An encrypted PGP message consists of 2 parts, or <I
CLASS="FIRSTTERM"
>packets</I
>:
</P
><P
></P
><UL
><LI
><P
> Packet containing a session key — either symmetric-key or public-key
encrypted.
</P
></LI
><LI
><P
> Packet containing data encrypted with the session key.
</P
></LI
></UL
><P
> When encrypting with a symmetric key (i.e., a password):
</P
><P
></P
><OL
TYPE="1"
><LI
><P
> The given password is hashed using a String2Key (S2K) algorithm. This is
rather similar to <CODE
CLASS="FUNCTION"
>crypt()</CODE
> algorithms — purposefully
slow and with random salt — but it produces a full-length binary
key.
</P
></LI
><LI
><P
> If a separate session key is requested, a new random key will be
generated. Otherwise the S2K key will be used directly as the session
key.
</P
></LI
><LI
><P
> If the S2K key is to be used directly, then only S2K settings will be put
into the session key packet. Otherwise the session key will be encrypted
with the S2K key and put into the session key packet.
</P
></LI
></OL
><P
> When encrypting with a public key:
</P
><P
></P
><OL
TYPE="1"
><LI
><P
> A new random session key is generated.
</P
></LI
><LI
><P
> It is encrypted using the public key and put into the session key packet.
</P
></LI
></OL
><P
> In either case the data to be encrypted is processed as follows:
</P
><P
></P
><OL
TYPE="1"
><LI
><P
> Optional data-manipulation: compression, conversion to UTF-8,
and/or conversion of line-endings.
</P
></LI
><LI
><P
> The data is prefixed with a block of random bytes. This is equivalent
to using a random IV.
</P
></LI
><LI
><P
> An SHA1 hash of the random prefix and data is appended.
</P
></LI
><LI
><P
> All this is encrypted with the session key and placed in the data packet.
</P
></LI
></OL
><DIV
CLASS="SECT3"
><H3
CLASS="SECT3"
><A
NAME="AEN150461"
>F.25.3.1. <CODE
CLASS="FUNCTION"
>pgp_sym_encrypt()</CODE
></A
></H3
><PRE
CLASS="SYNOPSIS"
>pgp_sym_encrypt(data text, psw text [, options text ]) returns bytea
pgp_sym_encrypt_bytea(data bytea, psw text [, options text ]) returns bytea</PRE
><P
> Encrypt <TT
CLASS="PARAMETER"
>data</TT
> with a symmetric PGP key <TT
CLASS="PARAMETER"
>psw</TT
>.
The <TT
CLASS="PARAMETER"
>options</TT
> parameter can contain option settings,
as described below.
</P
></DIV
><DIV
CLASS="SECT3"
><H3
CLASS="SECT3"
><A
NAME="AEN150469"
>F.25.3.2. <CODE
CLASS="FUNCTION"
>pgp_sym_decrypt()</CODE
></A
></H3
><PRE
CLASS="SYNOPSIS"
>pgp_sym_decrypt(msg bytea, psw text [, options text ]) returns text
pgp_sym_decrypt_bytea(msg bytea, psw text [, options text ]) returns bytea</PRE
><P
> Decrypt a symmetric-key-encrypted PGP message.
</P
><P
> Decrypting <TT
CLASS="TYPE"
>bytea</TT
> data with <CODE
CLASS="FUNCTION"
>pgp_sym_decrypt</CODE
> is disallowed.
This is to avoid outputting invalid character data. Decrypting
originally textual data with <CODE
CLASS="FUNCTION"
>pgp_sym_decrypt_bytea</CODE
> is fine.
</P
><P
> The <TT
CLASS="PARAMETER"
>options</TT
> parameter can contain option settings,
as described below.
</P
></DIV
><DIV
CLASS="SECT3"
><H3
CLASS="SECT3"
><A
NAME="AEN150480"
>F.25.3.3. <CODE
CLASS="FUNCTION"
>pgp_pub_encrypt()</CODE
></A
></H3
><PRE
CLASS="SYNOPSIS"
>pgp_pub_encrypt(data text, key bytea [, options text ]) returns bytea
pgp_pub_encrypt_bytea(data bytea, key bytea [, options text ]) returns bytea</PRE
><P
> Encrypt <TT
CLASS="PARAMETER"
>data</TT
> with a public PGP key <TT
CLASS="PARAMETER"
>key</TT
>.
Giving this function a secret key will produce an error.
</P
><P
> The <TT
CLASS="PARAMETER"
>options</TT
> parameter can contain option settings,
as described below.
</P
></DIV
><DIV
CLASS="SECT3"
><H3
CLASS="SECT3"
><A
NAME="AEN150489"
>F.25.3.4. <CODE
CLASS="FUNCTION"
>pgp_pub_decrypt()</CODE
></A
></H3
><PRE
CLASS="SYNOPSIS"
>pgp_pub_decrypt(msg bytea, key bytea [, psw text [, options text ]]) returns text
pgp_pub_decrypt_bytea(msg bytea, key bytea [, psw text [, options text ]]) returns bytea</PRE
><P
> Decrypt a public-key-encrypted message. <TT
CLASS="PARAMETER"
>key</TT
> must be the
secret key corresponding to the public key that was used to encrypt.
If the secret key is password-protected, you must give the password in
<TT
CLASS="PARAMETER"
>psw</TT
>. If there is no password, but you want to specify
options, you need to give an empty password.
</P
><P
> Decrypting <TT
CLASS="TYPE"
>bytea</TT
> data with <CODE
CLASS="FUNCTION"
>pgp_pub_decrypt</CODE
> is disallowed.
This is to avoid outputting invalid character data. Decrypting
originally textual data with <CODE
CLASS="FUNCTION"
>pgp_pub_decrypt_bytea</CODE
> is fine.
</P
><P
> The <TT
CLASS="PARAMETER"
>options</TT
> parameter can contain option settings,
as described below.
</P
></DIV
><DIV
CLASS="SECT3"
><H3
CLASS="SECT3"
><A
NAME="AEN150502"
>F.25.3.5. <CODE
CLASS="FUNCTION"
>pgp_key_id()</CODE
></A
></H3
><PRE
CLASS="SYNOPSIS"
>pgp_key_id(bytea) returns text</PRE
><P
> <CODE
CLASS="FUNCTION"
>pgp_key_id</CODE
> extracts the key ID of a PGP public or secret key.
Or it gives the key ID that was used for encrypting the data, if given
an encrypted message.
</P
><P
> It can return 2 special key IDs:
</P
><P
></P
><UL
><LI
><P
> <TT
CLASS="LITERAL"
>SYMKEY</TT
>
</P
><P
> The message is encrypted with a symmetric key.
</P
></LI
><LI
><P
> <TT
CLASS="LITERAL"
>ANYKEY</TT
>
</P
><P
> The message is public-key encrypted, but the key ID has been removed.
That means you will need to try all your secret keys on it to see
which one decrypts it. <TT
CLASS="FILENAME"
>pgcrypto</TT
> itself does not produce
such messages.
</P
></LI
></UL
><P
> Note that different keys may have the same ID. This is rare but a normal
event. The client application should then try to decrypt with each one,
to see which fits — like handling <TT
CLASS="LITERAL"
>ANYKEY</TT
>.
</P
></DIV
><DIV
CLASS="SECT3"
><H3
CLASS="SECT3"
><A
NAME="AEN150521"
>F.25.3.6. <CODE
CLASS="FUNCTION"
>armor()</CODE
>, <CODE
CLASS="FUNCTION"
>dearmor()</CODE
></A
></H3
><PRE
CLASS="SYNOPSIS"
>armor(data bytea) returns text
dearmor(data text) returns bytea</PRE
><P
> These functions wrap/unwrap binary data into PGP ASCII-armor format,
which is basically Base64 with CRC and additional formatting.
</P
></DIV
><DIV
CLASS="SECT3"
><H3
CLASS="SECT3"
><A
NAME="AEN150527"
>F.25.3.7. Options for PGP Functions</A
></H3
><P
> Options are named to be similar to GnuPG. An option's value should be
given after an equal sign; separate options from each other with commas.
For example:
</P><PRE
CLASS="PROGRAMLISTING"
>pgp_sym_encrypt(data, psw, 'compress-algo=1, cipher-algo=aes256')</PRE
><P>
</P
><P
> All of the options except <TT
CLASS="LITERAL"
>convert-crlf</TT
> apply only to
encrypt functions. Decrypt functions get the parameters from the PGP
data.
</P
><P
> The most interesting options are probably
<TT
CLASS="LITERAL"
>compress-algo</TT
> and <TT
CLASS="LITERAL"
>unicode-mode</TT
>.
The rest should have reasonable defaults.
</P
><DIV
CLASS="SECT4"
><H4
CLASS="SECT4"
><A
NAME="AEN150536"
>F.25.3.7.1. cipher-algo</A
></H4
><P
> Which cipher algorithm to use.
</P
><P
CLASS="LITERALLAYOUT"
>Values: bf, aes128, aes192, aes256 (OpenSSL-only: <TT
CLASS="LITERAL"
>3des</TT
>, <TT
CLASS="LITERAL"
>cast5</TT
>)<br>
Default: aes128<br>
Applies to: pgp_sym_encrypt, pgp_pub_encrypt</P
></DIV
><DIV
CLASS="SECT4"
><H4
CLASS="SECT4"
><A
NAME="AEN150542"
>F.25.3.7.2. compress-algo</A
></H4
><P
> Which compression algorithm to use. Only available if
<SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> was built with zlib.
</P
><P
CLASS="LITERALLAYOUT"
>Values:<br>
0 - no compression<br>
1 - ZIP compression<br>
2 - ZLIB compression (= ZIP plus meta-data and block CRCs)<br>
Default: 0<br>
Applies to: pgp_sym_encrypt, pgp_pub_encrypt</P
></DIV
><DIV
CLASS="SECT4"
><H4
CLASS="SECT4"
><A
NAME="AEN150547"
>F.25.3.7.3. compress-level</A
></H4
><P
> How much to compress. Higher levels compress smaller but are slower.
0 disables compression.
</P
><P
CLASS="LITERALLAYOUT"
>Values: 0, 1-9<br>
Default: 6<br>
Applies to: pgp_sym_encrypt, pgp_pub_encrypt</P
></DIV
><DIV
CLASS="SECT4"
><H4
CLASS="SECT4"
><A
NAME="AEN150551"
>F.25.3.7.4. convert-crlf</A
></H4
><P
> Whether to convert <TT
CLASS="LITERAL"
>\n</TT
> into <TT
CLASS="LITERAL"
>\r\n</TT
> when
encrypting and <TT
CLASS="LITERAL"
>\r\n</TT
> to <TT
CLASS="LITERAL"
>\n</TT
> when
decrypting. RFC 4880 specifies that text data should be stored using
<TT
CLASS="LITERAL"
>\r\n</TT
> line-feeds. Use this to get fully RFC-compliant
behavior.
</P
><P
CLASS="LITERALLAYOUT"
>Values: 0, 1<br>
Default: 0<br>
Applies to: pgp_sym_encrypt, pgp_pub_encrypt, pgp_sym_decrypt, pgp_pub_decrypt</P
></DIV
><DIV
CLASS="SECT4"
><H4
CLASS="SECT4"
><A
NAME="AEN150560"
>F.25.3.7.5. disable-mdc</A
></H4
><P
> Do not protect data with SHA-1. The only good reason to use this
option is to achieve compatibility with ancient PGP products, predating
the addition of SHA-1 protected packets to RFC 4880.
Recent gnupg.org and pgp.com software supports it fine.
</P
><P
CLASS="LITERALLAYOUT"
>Values: 0, 1<br>
Default: 0<br>
Applies to: pgp_sym_encrypt, pgp_pub_encrypt</P
></DIV
><DIV
CLASS="SECT4"
><H4
CLASS="SECT4"
><A
NAME="AEN150564"
>F.25.3.7.6. sess-key</A
></H4
><P
> Use separate session key. Public-key encryption always uses a separate
session key; this option is for symmetric-key encryption, which by default
uses the S2K key directly.
</P
><P
CLASS="LITERALLAYOUT"
>Values: 0, 1<br>
Default: 0<br>
Applies to: pgp_sym_encrypt</P
></DIV
><DIV
CLASS="SECT4"
><H4
CLASS="SECT4"
><A
NAME="AEN150568"
>F.25.3.7.7. s2k-mode</A
></H4
><P
> Which S2K algorithm to use.
</P
><P
CLASS="LITERALLAYOUT"
>Values:<br>
0 - Without salt. Dangerous!<br>
1 - With salt but with fixed iteration count.<br>
3 - Variable iteration count.<br>
Default: 3<br>
Applies to: pgp_sym_encrypt</P
></DIV
><DIV
CLASS="SECT4"
><H4
CLASS="SECT4"
><A
NAME="AEN150572"
>F.25.3.7.8. s2k-digest-algo</A
></H4
><P
> Which digest algorithm to use in S2K calculation.
</P
><P
CLASS="LITERALLAYOUT"
>Values: md5, sha1<br>
Default: sha1<br>
Applies to: pgp_sym_encrypt</P
></DIV
><DIV
CLASS="SECT4"
><H4
CLASS="SECT4"
><A
NAME="AEN150576"
>F.25.3.7.9. s2k-cipher-algo</A
></H4
><P
> Which cipher to use for encrypting separate session key.
</P
><P
CLASS="LITERALLAYOUT"
>Values: bf, aes, aes128, aes192, aes256<br>
Default: use cipher-algo<br>
Applies to: pgp_sym_encrypt</P
></DIV
><DIV
CLASS="SECT4"
><H4
CLASS="SECT4"
><A
NAME="AEN150580"
>F.25.3.7.10. unicode-mode</A
></H4
><P
> Whether to convert textual data from database internal encoding to
UTF-8 and back. If your database already is UTF-8, no conversion will
be done, but the message will be tagged as UTF-8. Without this option
it will not be.
</P
><P
CLASS="LITERALLAYOUT"
>Values: 0, 1<br>
Default: 0<br>
Applies to: pgp_sym_encrypt, pgp_pub_encrypt</P
></DIV
></DIV
><DIV
CLASS="SECT3"
><H3
CLASS="SECT3"
><A
NAME="AEN150584"
>F.25.3.8. Generating PGP Keys with GnuPG</A
></H3
><P
> To generate a new key:
</P><PRE
CLASS="PROGRAMLISTING"
>gpg --gen-key</PRE
><P>
</P
><P
> The preferred key type is <SPAN
CLASS="QUOTE"
>"DSA and Elgamal"</SPAN
>.
</P
><P
> For RSA encryption you must create either DSA or RSA sign-only key
as master and then add an RSA encryption subkey with
<TT
CLASS="LITERAL"
>gpg --edit-key</TT
>.
</P
><P
> To list keys:
</P><PRE
CLASS="PROGRAMLISTING"
>gpg --list-secret-keys</PRE
><P>
</P
><P
> To export a public key in ASCII-armor format:
</P><PRE
CLASS="PROGRAMLISTING"
>gpg -a --export KEYID > public.key</PRE
><P>
</P
><P
> To export a secret key in ASCII-armor format:
</P><PRE
CLASS="PROGRAMLISTING"
>gpg -a --export-secret-keys KEYID > secret.key</PRE
><P>
</P
><P
> You need to use <CODE
CLASS="FUNCTION"
>dearmor()</CODE
> on these keys before giving them to
the PGP functions. Or if you can handle binary data, you can drop
<TT
CLASS="LITERAL"
>-a</TT
> from the command.
</P
><P
> For more details see <TT
CLASS="LITERAL"
>man gpg</TT
>,
<A
HREF="http://www.gnupg.org/gph/en/manual.html"
TARGET="_top"
>The GNU
Privacy Handbook</A
> and other documentation on
<A
HREF="http://www.gnupg.org"
TARGET="_top"
>http://www.gnupg.org</A
>.
</P
></DIV
><DIV
CLASS="SECT3"
><H3
CLASS="SECT3"
><A
NAME="AEN150605"
>F.25.3.9. Limitations of PGP Code</A
></H3
><P
></P
><UL
><LI
><P
> No support for signing. That also means that it is not checked
whether the encryption subkey belongs to the master key.
</P
></LI
><LI
><P
> No support for encryption key as master key. As such practice
is generally discouraged, this should not be a problem.
</P
></LI
><LI
><P
> No support for several subkeys. This may seem like a problem, as this
is common practice. On the other hand, you should not use your regular
GPG/PGP keys with <TT
CLASS="FILENAME"
>pgcrypto</TT
>, but create new ones,
as the usage scenario is rather different.
</P
></LI
></UL
></DIV
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN150615"
>F.25.4. Raw Encryption Functions</A
></H2
><P
> These functions only run a cipher over data; they don't have any advanced
features of PGP encryption. Therefore they have some major problems:
</P
><P
></P
><OL
TYPE="1"
><LI
><P
> They use user key directly as cipher key.
</P
></LI
><LI
><P
> They don't provide any integrity checking, to see
if the encrypted data was modified.
</P
></LI
><LI
><P
> They expect that users manage all encryption parameters
themselves, even IV.
</P
></LI
><LI
><P
> They don't handle text.
</P
></LI
></OL
><P
> So, with the introduction of PGP encryption, usage of raw
encryption functions is discouraged.
</P
><PRE
CLASS="SYNOPSIS"
>encrypt(data bytea, key bytea, type text) returns bytea
decrypt(data bytea, key bytea, type text) returns bytea
encrypt_iv(data bytea, key bytea, iv bytea, type text) returns bytea
decrypt_iv(data bytea, key bytea, iv bytea, type text) returns bytea</PRE
><P
> Encrypt/decrypt data using the cipher method specified by
<TT
CLASS="PARAMETER"
>type</TT
>. The syntax of the
<TT
CLASS="PARAMETER"
>type</TT
> string is:
</P><PRE
CLASS="SYNOPSIS"
><TT
CLASS="REPLACEABLE"
><I
>algorithm</I
></TT
> [<SPAN
CLASS="OPTIONAL"
> <TT
CLASS="LITERAL"
>-</TT
> <TT
CLASS="REPLACEABLE"
><I
>mode</I
></TT
> </SPAN
>] [<SPAN
CLASS="OPTIONAL"
> <TT
CLASS="LITERAL"
>/pad:</TT
> <TT
CLASS="REPLACEABLE"
><I
>padding</I
></TT
> </SPAN
>]</PRE
><P>
where <TT
CLASS="REPLACEABLE"
><I
>algorithm</I
></TT
> is one of:
<P
></P
></P><UL
><LI
><P
><TT
CLASS="LITERAL"
>bf</TT
> — Blowfish</P
></LI
><LI
><P
><TT
CLASS="LITERAL"
>aes</TT
> — AES (Rijndael-128)</P
></LI
></UL
><P>
and <TT
CLASS="REPLACEABLE"
><I
>mode</I
></TT
> is one of:
<P
></P
></P><UL
><LI
><P
> <TT
CLASS="LITERAL"
>cbc</TT
> — next block depends on previous (default)
</P
></LI
><LI
><P
> <TT
CLASS="LITERAL"
>ecb</TT
> — each block is encrypted separately (for
testing only)
</P
></LI
></UL
><P>
and <TT
CLASS="REPLACEABLE"
><I
>padding</I
></TT
> is one of:
<P
></P
></P><UL
><LI
><P
> <TT
CLASS="LITERAL"
>pkcs</TT
> — data may be any length (default)
</P
></LI
><LI
><P
> <TT
CLASS="LITERAL"
>none</TT
> — data must be multiple of cipher block size
</P
></LI
></UL
><P>
</P
><P
> So, for example, these are equivalent:
</P><PRE
CLASS="PROGRAMLISTING"
>encrypt(data, 'fooz', 'bf')
encrypt(data, 'fooz', 'bf-cbc/pad:pkcs')</PRE
><P>
</P
><P
> In <CODE
CLASS="FUNCTION"
>encrypt_iv</CODE
> and <CODE
CLASS="FUNCTION"
>decrypt_iv</CODE
>, the
<TT
CLASS="PARAMETER"
>iv</TT
> parameter is the initial value for the CBC mode;
it is ignored for ECB.
It is clipped or padded with zeroes if not exactly block size.
It defaults to all zeroes in the functions without this parameter.
</P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN150670"
>F.25.5. Random-Data Functions</A
></H2
><PRE
CLASS="SYNOPSIS"
>gen_random_bytes(count integer) returns bytea</PRE
><P
> Returns <TT
CLASS="PARAMETER"
>count</TT
> cryptographically strong random bytes.
At most 1024 bytes can be extracted at a time. This is to avoid
draining the randomness generator pool.
</P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN150675"
>F.25.6. Notes</A
></H2
><DIV
CLASS="SECT3"
><H3
CLASS="SECT3"
><A
NAME="AEN150677"
>F.25.6.1. Configuration</A
></H3
><P
> <TT
CLASS="FILENAME"
>pgcrypto</TT
> configures itself according to the findings of the
main PostgreSQL <TT
CLASS="LITERAL"
>configure</TT
> script. The options that
affect it are <TT
CLASS="LITERAL"
>--with-zlib</TT
> and
<TT
CLASS="LITERAL"
>--with-openssl</TT
>.
</P
><P
> When compiled with zlib, PGP encryption functions are able to
compress data before encrypting.
</P
><P
> When compiled with OpenSSL, there will be more algorithms available.
Also public-key encryption functions will be faster as OpenSSL
has more optimized BIGNUM functions.
</P
><DIV
CLASS="TABLE"
><A
NAME="PGCRYPTO-WITH-WITHOUT-OPENSSL"
></A
><P
><B
>Table F-20. Summary of Functionality with and without OpenSSL</B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><COL><COL><COL><THEAD
><TR
><TH
>Functionality</TH
><TH
>Built-in</TH
><TH
>With OpenSSL</TH
></TR
></THEAD
><TBODY
><TR
><TD
>MD5</TD
><TD
>yes</TD
><TD
>yes</TD
></TR
><TR
><TD
>SHA1</TD
><TD
>yes</TD
><TD
>yes</TD
></TR
><TR
><TD
>SHA224/256/384/512</TD
><TD
>yes</TD
><TD
>yes (Note 1)</TD
></TR
><TR
><TD
>Other digest algorithms</TD
><TD
>no</TD
><TD
>yes (Note 2)</TD
></TR
><TR
><TD
>Blowfish</TD
><TD
>yes</TD
><TD
>yes</TD
></TR
><TR
><TD
>AES</TD
><TD
>yes</TD
><TD
>yes (Note 3)</TD
></TR
><TR
><TD
>DES/3DES/CAST5</TD
><TD
>no</TD
><TD
>yes</TD
></TR
><TR
><TD
>Raw encryption</TD
><TD
>yes</TD
><TD
>yes</TD
></TR
><TR
><TD
>PGP Symmetric encryption</TD
><TD
>yes</TD
><TD
>yes</TD
></TR
><TR
><TD
>PGP Public-Key encryption</TD
><TD
>yes</TD
><TD
>yes</TD
></TR
></TBODY
></TABLE
></DIV
><P
> Notes:
</P
><P
></P
><OL
TYPE="1"
><LI
><P
> SHA2 algorithms were added to OpenSSL in version 0.9.8. For
older versions, <TT
CLASS="FILENAME"
>pgcrypto</TT
> will use built-in code.
</P
></LI
><LI
><P
> Any digest algorithm OpenSSL supports is automatically picked up.
This is not possible with ciphers, which need to be supported
explicitly.
</P
></LI
><LI
><P
> AES is included in OpenSSL since version 0.9.7. For
older versions, <TT
CLASS="FILENAME"
>pgcrypto</TT
> will use built-in code.
</P
></LI
></OL
></DIV
><DIV
CLASS="SECT3"
><H3
CLASS="SECT3"
><A
NAME="AEN150745"
>F.25.6.2. NULL Handling</A
></H3
><P
> As is standard in SQL, all functions return NULL, if any of the arguments
are NULL. This may create security risks on careless usage.
</P
></DIV
><DIV
CLASS="SECT3"
><H3
CLASS="SECT3"
><A
NAME="AEN150748"
>F.25.6.3. Security Limitations</A
></H3
><P
> All <TT
CLASS="FILENAME"
>pgcrypto</TT
> functions run inside the database server.
That means that all
the data and passwords move between <TT
CLASS="FILENAME"
>pgcrypto</TT
> and client
applications in clear text. Thus you must:
</P
><P
></P
><OL
TYPE="1"
><LI
><P
>Connect locally or use SSL connections.</P
></LI
><LI
><P
>Trust both system and database administrator.</P
></LI
></OL
><P
> If you cannot, then better do crypto inside client application.
</P
><P
> The implementation does not resist
<A
HREF="http://en.wikipedia.org/wiki/Side-channel_attack"
TARGET="_top"
>side-channel
attacks</A
>. For example, the time required for
a <TT
CLASS="FILENAME"
>pgcrypto</TT
> decryption function to complete varies among
ciphertexts of a given size.
</P
></DIV
><DIV
CLASS="SECT3"
><H3
CLASS="SECT3"
><A
NAME="AEN150762"
>F.25.6.4. Useful Reading</A
></H3
><P
></P
><UL
><LI
><P
><A
HREF="http://www.gnupg.org/gph/en/manual.html"
TARGET="_top"
>http://www.gnupg.org/gph/en/manual.html</A
></P
><P
>The GNU Privacy Handbook.</P
></LI
><LI
><P
><A
HREF="http://www.openwall.com/crypt/"
TARGET="_top"
>http://www.openwall.com/crypt/</A
></P
><P
>Describes the crypt-blowfish algorithm.</P
></LI
><LI
><P
> <A
HREF="http://www.stack.nl/~galactus/remailers/passphrase-faq.html"
TARGET="_top"
>http://www.stack.nl/~galactus/remailers/passphrase-faq.html</A
>
</P
><P
>How to choose a good password.</P
></LI
><LI
><P
><A
HREF="http://world.std.com/~reinhold/diceware.html"
TARGET="_top"
>http://world.std.com/~reinhold/diceware.html</A
></P
><P
>Interesting idea for picking passwords.</P
></LI
><LI
><P
> <A
HREF="http://www.interhack.net/people/cmcurtin/snake-oil-faq.html"
TARGET="_top"
>http://www.interhack.net/people/cmcurtin/snake-oil-faq.html</A
>
</P
><P
>Describes good and bad cryptography.</P
></LI
></UL
></DIV
><DIV
CLASS="SECT3"
><H3
CLASS="SECT3"
><A
NAME="AEN150785"
>F.25.6.5. Technical References</A
></H3
><P
></P
><UL
><LI
><P
><A
HREF="http://www.ietf.org/rfc/rfc4880.txt"
TARGET="_top"
>http://www.ietf.org/rfc/rfc4880.txt</A
></P
><P
>OpenPGP message format.</P
></LI
><LI
><P
><A
HREF="http://www.ietf.org/rfc/rfc1321.txt"
TARGET="_top"
>http://www.ietf.org/rfc/rfc1321.txt</A
></P
><P
>The MD5 Message-Digest Algorithm.</P
></LI
><LI
><P
><A
HREF="http://www.ietf.org/rfc/rfc2104.txt"
TARGET="_top"
>http://www.ietf.org/rfc/rfc2104.txt</A
></P
><P
>HMAC: Keyed-Hashing for Message Authentication.</P
></LI
><LI
><P
> <A
HREF="http://www.usenix.org/events/usenix99/provos.html"
TARGET="_top"
>http://www.usenix.org/events/usenix99/provos.html</A
>
</P
><P
>Comparison of crypt-des, crypt-md5 and bcrypt algorithms.</P
></LI
><LI
><P
><A
HREF="http://csrc.nist.gov/cryptval/des.htm"
TARGET="_top"
>http://csrc.nist.gov/cryptval/des.htm</A
></P
><P
>Standards for DES, 3DES and AES.</P
></LI
><LI
><P
> <A
HREF="http://en.wikipedia.org/wiki/Fortuna_(PRNG)"
TARGET="_top"
>http://en.wikipedia.org/wiki/Fortuna_(PRNG)</A
>
</P
><P
>Description of Fortuna CSPRNG.</P
></LI
><LI
><P
><A
HREF="http://jlcooke.ca/random/"
TARGET="_top"
>http://jlcooke.ca/random/</A
></P
><P
>Jean-Luc Cooke Fortuna-based <TT
CLASS="FILENAME"
>/dev/random</TT
> driver for Linux.</P
></LI
><LI
><P
><A
HREF="http://research.cyber.ee/~lipmaa/crypto/"
TARGET="_top"
>http://research.cyber.ee/~lipmaa/crypto/</A
></P
><P
>Collection of cryptology pointers.</P
></LI
></UL
></DIV
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN150821"
>F.25.7. Author</A
></H2
><P
> Marko Kreen <CODE
CLASS="EMAIL"
><<A
HREF="mailto:markokr@gmail.com"
>markokr@gmail.com</A
>></CODE
>
</P
><P
> <TT
CLASS="FILENAME"
>pgcrypto</TT
> uses code from the following sources:
</P
><DIV
CLASS="INFORMALTABLE"
><P
></P
><A
NAME="AEN150827"
></A
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><COL><COL><COL><THEAD
><TR
><TH
>Algorithm</TH
><TH
>Author</TH
><TH
>Source origin</TH
></TR
></THEAD
><TBODY
><TR
><TD
>DES crypt</TD
><TD
>David Burren and others</TD
><TD
>FreeBSD libcrypt</TD
></TR
><TR
><TD
>MD5 crypt</TD
><TD
>Poul-Henning Kamp</TD
><TD
>FreeBSD libcrypt</TD
></TR
><TR
><TD
>Blowfish crypt</TD
><TD
>Solar Designer</TD
><TD
>www.openwall.com</TD
></TR
><TR
><TD
>Blowfish cipher</TD
><TD
>Simon Tatham</TD
><TD
>PuTTY</TD
></TR
><TR
><TD
>Rijndael cipher</TD
><TD
>Brian Gladman</TD
><TD
>OpenBSD sys/crypto</TD
></TR
><TR
><TD
>MD5 and SHA1</TD
><TD
>WIDE Project</TD
><TD
>KAME kame/sys/crypto</TD
></TR
><TR
><TD
>SHA256/384/512 </TD
><TD
>Aaron D. Gifford</TD
><TD
>OpenBSD sys/crypto</TD
></TR
><TR
><TD
>BIGNUM math</TD
><TD
>Michael J. Fromberger</TD
><TD
>dartmouth.edu/~sting/sw/imath</TD
></TR
></TBODY
></TABLE
><P
></P
></DIV
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