<?xml version="1.0" encoding="latin1" ?>
<!DOCTYPE erlref SYSTEM "erlref.dtd">
<erlref>
<header>
<copyright>
<year>1999</year><year>2009</year>
<holder>Ericsson AB. All Rights Reserved.</holder>
</copyright>
<legalnotice>
The contents of this file are subject to the Erlang Public License,
Version 1.1, (the "License"); you may not use this file except in
compliance with the License. You should have received a copy of the
Erlang Public License along with this software. If not, it can be
retrieved online at http://www.erlang.org/.
Software distributed under the License is distributed on an "AS IS"
basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
the License for the specific language governing rights and limitations
under the License.
</legalnotice>
<title>crypto</title>
<prepared>Peter Högfeldt</prepared>
<docno></docno>
<date>2000-06-20</date>
<rev>B</rev>
</header>
<module>crypto</module>
<modulesummary>Crypto Functions</modulesummary>
<description>
<p>This module provides a set of cryptographic functions.
</p>
<p>References:</p>
<list type="bulleted">
<item>
<p>md5: The MD5 Message Digest Algorithm (RFC 1321)</p>
</item>
<item>
<p>sha: Secure Hash Standard (FIPS 180-2)</p>
</item>
<item>
<p>hmac: Keyed-Hashing for Message Authentication (RFC 2104)</p>
</item>
<item>
<p>des: Data Encryption Standard (FIPS 46-3)</p>
</item>
<item>
<p>aes: Advanced Encryption Standard (AES) (FIPS 197) </p>
</item>
<item>
<p>ecb, cbc, cfb, ofb: Recommendation for Block Cipher Modes
of Operation (NIST SP 800-38A).</p>
</item>
<item>
<p>rsa: Recommendation for Block Cipher Modes of Operation
(NIST 800-38A)</p>
</item>
<item>
<p>dss: Digital Signature Standard (FIPS 186-2)</p>
</item>
</list>
<p>The above publications can be found at <url href="http://csrc.nist.gov/publications">NIST publications</url>, at <url href="http://www.ietf.org">IETF</url>.
</p>
<p><em>Types</em></p>
<pre>
byte() = 0 ... 255
ioelem() = byte() | binary() | iolist()
iolist() = [ioelem()]
Mpint() = <![CDATA[<<ByteLen:32/integer-big, Bytes:ByteLen/binary>>]]>
</pre>
<p></p>
</description>
<funcs>
<func>
<name>start() -> ok</name>
<fsummary>Start the crypto server.</fsummary>
<desc>
<p>Starts the crypto server.</p>
</desc>
</func>
<func>
<name>stop() -> ok</name>
<fsummary>Stop the crypto server.</fsummary>
<desc>
<p>Stops the crypto server.</p>
</desc>
</func>
<func>
<name>info() -> [atom()]</name>
<fsummary>Provide a list of available crypto functions.</fsummary>
<desc>
<p>Provides the available crypto functions in terms of a list
of atoms.</p>
</desc>
</func>
<func>
<name>info_lib() -> [{Name,VerNum,VerStr}]</name>
<fsummary>Provides information about the libraries used by crypto.</fsummary>
<type>
<v>Name = binary()</v>
<v>VerNum = integer()</v>
<v>VerStr = binary()</v>
</type>
<desc>
<p>Provides the name and version of the libraries used by crypto.</p>
<p><c>Name</c> is the name of the library. <c>VerNum</c> is
the numeric version according to the library's own versioning
scheme. <c>VerStr</c> contains a text variant of the version.</p>
<pre>
> <input>info_lib().</input>
[{<<"OpenSSL">>,9469983,<<"OpenSSL 0.9.8a 11 Oct 2005">>}]
</pre>
</desc>
</func>
<func>
<name>md5(Data) -> Digest</name>
<fsummary>Compute an <c>MD5</c>message digest from <c>Data</c></fsummary>
<type>
<v>Data = iolist() | binary()</v>
<v>Digest = binary()</v>
</type>
<desc>
<p>Computes an <c>MD5</c> message digest from <c>Data</c>, where
the length of the digest is 128 bits (16 bytes).</p>
</desc>
</func>
<func>
<name>md5_init() -> Context</name>
<fsummary>Creates an MD5 context</fsummary>
<type>
<v>Context = binary()</v>
</type>
<desc>
<p>Creates an MD5 context, to be used in subsequent calls to
<c>md5_update/2</c>.</p>
</desc>
</func>
<func>
<name>md5_update(Context, Data) -> NewContext</name>
<fsummary>Update an MD5 <c>Context</c>with <c>Data</c>, and return a <c>NewContext</c></fsummary>
<type>
<v>Data = iolist() | binary()</v>
<v>Context = NewContext = binary()</v>
</type>
<desc>
<p>Updates an MD5 <c>Context</c> with <c>Data</c>, and returns
a <c>NewContext</c>.</p>
</desc>
</func>
<func>
<name>md5_final(Context) -> Digest</name>
<fsummary>Finish the update of an MD5 <c>Context</c>and return the computed <c>MD5</c>message digest</fsummary>
<type>
<v>Context = Digest = binary()</v>
</type>
<desc>
<p>Finishes the update of an MD5 <c>Context</c> and returns
the computed <c>MD5</c> message digest.</p>
</desc>
</func>
<func>
<name>sha(Data) -> Digest</name>
<fsummary>Compute an <c>SHA</c>message digest from <c>Data</c></fsummary>
<type>
<v>Data = iolist() | binary()</v>
<v>Digest = binary()</v>
</type>
<desc>
<p>Computes an <c>SHA</c> message digest from <c>Data</c>, where
the length of the digest is 160 bits (20 bytes).</p>
</desc>
</func>
<func>
<name>sha_init() -> Context</name>
<fsummary>Create an SHA context</fsummary>
<type>
<v>Context = binary()</v>
</type>
<desc>
<p>Creates an SHA context, to be used in subsequent calls to
<c>sha_update/2</c>.</p>
</desc>
</func>
<func>
<name>sha_update(Context, Data) -> NewContext</name>
<fsummary>Update an SHA context</fsummary>
<type>
<v>Data = iolist() | binary()</v>
<v>Context = NewContext = binary()</v>
</type>
<desc>
<p>Updates an SHA <c>Context</c> with <c>Data</c>, and returns
a <c>NewContext</c>.</p>
</desc>
</func>
<func>
<name>sha_final(Context) -> Digest</name>
<fsummary>Finish the update of an SHA context</fsummary>
<type>
<v>Context = Digest = binary()</v>
</type>
<desc>
<p>Finishes the update of an SHA <c>Context</c> and returns
the computed <c>SHA</c> message digest.</p>
</desc>
</func>
<func>
<name>md5_mac(Key, Data) -> Mac</name>
<fsummary>Compute an <c>MD5 MAC</c>message authentification code</fsummary>
<type>
<v>Key = Data = iolist() | binary()</v>
<v>Mac = binary()</v>
</type>
<desc>
<p>Computes an <c>MD5 MAC</c> message authentification code
from <c>Key</c> and <c>Data</c>, where the the length of the
Mac is 128 bits (16 bytes).</p>
</desc>
</func>
<func>
<name>md5_mac_96(Key, Data) -> Mac</name>
<fsummary>Compute an <c>MD5 MAC</c>message authentification code</fsummary>
<type>
<v>Key = Data = iolist() | binary()</v>
<v>Mac = binary()</v>
</type>
<desc>
<p>Computes an <c>MD5 MAC</c> message authentification code
from <c>Key</c> and <c>Data</c>, where the length of the Mac
is 96 bits (12 bytes).</p>
</desc>
</func>
<func>
<name>sha_mac(Key, Data) -> Mac</name>
<fsummary>Compute an <c>MD5 MAC</c>message authentification code</fsummary>
<type>
<v>Key = Data = iolist() | binary()</v>
<v>Mac = binary()</v>
</type>
<desc>
<p>Computes an <c>SHA MAC</c> message authentification code
from <c>Key</c> and <c>Data</c>, where the length of the Mac
is 160 bits (20 bytes).</p>
</desc>
</func>
<func>
<name>sha_mac_96(Key, Data) -> Mac</name>
<fsummary>Compute an <c>MD5 MAC</c>message authentification code</fsummary>
<type>
<v>Key = Data = iolist() | binary()</v>
<v>Mac = binary()</v>
</type>
<desc>
<p>Computes an <c>SHA MAC</c> message authentification code
from <c>Key</c> and <c>Data</c>, where the length of the Mac
is 96 bits (12 bytes).</p>
</desc>
</func>
<func>
<name>des_cbc_encrypt(Key, IVec, Text) -> Cipher</name>
<fsummary>Encrypt <c>Text</c>according to DES in CBC mode</fsummary>
<type>
<v>Key = Text = iolist() | binary()</v>
<v>IVec = Cipher = binary()</v>
</type>
<desc>
<p>Encrypts <c>Text</c> according to DES in CBC
mode. <c>Text</c> must be a multiple of 64 bits (8
bytes). <c>Key</c> is the DES key, and <c>IVec</c> is an
arbitrary initializing vector. The lengths of <c>Key</c> and
<c>IVec</c> must be 64 bits (8 bytes).</p>
</desc>
</func>
<func>
<name>des_cbc_decrypt(Key, IVec, Cipher) -> Text</name>
<fsummary>Decrypt <c>Cipher</c>according to DES in CBC mode</fsummary>
<type>
<v>Key = Cipher = iolist() | binary()</v>
<v>IVec = Text = binary()</v>
</type>
<desc>
<p>Decrypts <c>Cipher</c> according to DES in CBC mode.
<c>Key</c> is the DES key, and <c>IVec</c> is an arbitrary
initializing vector. <c>Key</c> and <c>IVec</c> must have
the same values as those used when encrypting. <c>Cipher</c>
must be a multiple of 64 bits (8 bytes). The lengths of
<c>Key</c> and <c>IVec</c> must be 64 bits (8 bytes).</p>
</desc>
</func>
<func>
<name>des_cbc_ivec(Data) -> IVec</name>
<fsummary>Get <c>IVec</c> to be used in next iteration of
<c>des_cbc_[ecrypt|decrypt]</c></fsummary>
<type>
<v>Data = iolist() | binary()</v>
<v>IVec = binary()</v>
</type>
<desc>
<p>Returns the <c>IVec</c> to be used in a next iteration of
<c>des_cbc_[encrypt|decrypt]</c>. <c>Data</c> is the encrypted
data from the previous iteration step.</p>
</desc>
</func>
<func>
<name>des3_cbc_encrypt(Key1, Key2, Key3, IVec, Text) -> Cipher</name>
<fsummary>Encrypt <c>Text</c>according to DES3 in CBC mode</fsummary>
<type>
<v>Key1 =Key2 = Key3 Text = iolist() | binary()</v>
<v>IVec = Cipher = binary()</v>
</type>
<desc>
<p>Encrypts <c>Text</c> according to DES3 in CBC
mode. <c>Text</c> must be a multiple of 64 bits (8
bytes). <c>Key1</c>, <c>Key2</c>, <c>Key3</c>, are the DES
keys, and <c>IVec</c> is an arbitrary initializing
vector. The lengths of each of <c>Key1</c>, <c>Key2</c>,
<c>Key3</c> and <c>IVec</c> must be 64 bits (8 bytes).</p>
</desc>
</func>
<func>
<name>des3_cbc_decrypt(Key1, Key2, Key3, IVec, Cipher) -> Text</name>
<fsummary>Decrypt <c>Cipher</c>according to DES in CBC mode</fsummary>
<type>
<v>Key1 = Key2 = Key3 = Cipher = iolist() | binary()</v>
<v>IVec = Text = binary()</v>
</type>
<desc>
<p>Decrypts <c>Cipher</c> according to DES3 in CBC mode.
<c>Key1</c>, <c>Key2</c>, <c>Key3</c> are the DES key, and
<c>IVec</c> is an arbitrary initializing vector.
<c>Key1</c>, <c>Key2</c>, <c>Key3</c> and <c>IVec</c> must
and <c>IVec</c> must have the same values as those used when
encrypting. <c>Cipher</c> must be a multiple of 64 bits (8
bytes). The lengths of <c>Key1</c>, <c>Key2</c>,
<c>Key3</c>, and <c>IVec</c> must be 64 bits (8 bytes).</p>
</desc>
</func>
<func>
<name>blowfish_cfb64_encrypt(Key, IVec, Text) -> Cipher</name>
<fsummary>Encrypt <c>Text</c>using Blowfish in CFB mode with 64
bit feedback</fsummary>
<type>
<v>Key = Text = iolist() | binary()</v>
<v>IVec = Cipher = binary()</v>
</type>
<desc>
<p>Encrypts <c>Text</c> using Blowfish in CFB mode with 64 bit
feedback. <c>Key</c> is the Blowfish key, and <c>IVec</c> is an
arbitrary initializing vector. The length of <c>IVec</c>
must be 64 bits (8 bytes).</p>
</desc>
</func>
<func>
<name>blowfish_cfb64_decrypt(Key, IVec, Text) -> Cipher</name>
<fsummary>Decrypt <c>Text</c>using Blowfish in CFB mode with 64
bit feedback</fsummary>
<type>
<v>Key = Text = iolist() | binary()</v>
<v>IVec = Cipher = binary()</v>
</type>
<desc>
<p>Decrypts <c>Text</c> using Blowfish in CFB mode with 64 bit
feedback. <c>Key</c> is the Blowfish key, and <c>IVec</c> is an
arbitrary initializing vector. The length of <c>IVec</c>
must be 64 bits (8 bytes).</p>
</desc>
</func>
<func>
<name>aes_cfb_128_encrypt(Key, IVec, Text) -> Cipher</name>
<name>aes_cbc_128_encrypt(Key, IVec, Text) -> Cipher</name>
<fsummary>Encrypt <c>Text</c>according to AES in Cipher Feedback mode or Cipher Block Chaining mode</fsummary>
<type>
<v>Key = Text = iolist() | binary()</v>
<v>IVec = Cipher = binary()</v>
</type>
<desc>
<p>Encrypts <c>Text</c> according to AES in Cipher Feedback
mode (CFB) or Cipher Block Chaining mode (CBC). <c>Text</c>
must be a multiple of 128 bits (16 bytes). <c>Key</c> is the
AES key, and <c>IVec</c> is an arbitrary initializing vector.
The lengths of <c>Key</c> and <c>IVec</c> must be 128 bits
(16 bytes).</p>
</desc>
</func>
<func>
<name>aes_cfb_128_decrypt(Key, IVec, Cipher) -> Text</name>
<name>aes_cbc_128_decrypt(Key, IVec, Cipher) -> Text</name>
<fsummary>Decrypt <c>Cipher</c>according to AES in Cipher Feedback mode or Cipher Block Chaining mode</fsummary>
<type>
<v>Key = Cipher = iolist() | binary()</v>
<v>IVec = Text = binary()</v>
</type>
<desc>
<p>Decrypts <c>Cipher</c> according to Cipher Feedback Mode (CFB)
or Cipher Block Chaining mode (CBC).
<c>Key</c> is the AES key, and <c>IVec</c> is an arbitrary
initializing vector. <c>Key</c> and <c>IVec</c> must have
the same values as those used when encrypting. <c>Cipher</c>
must be a multiple of 128 bits (16 bytes). The lengths of
<c>Key</c> and <c>IVec</c> must be 128 bits (16 bytes).</p>
</desc>
</func>
<func>
<name>aes_cbc_ivec(Data) -> IVec</name>
<fsummary>Get <c>IVec</c> to be used in next iteration of
<c>aes_cbc_*_[ecrypt|decrypt]</c></fsummary>
<type>
<v>Data = iolist() | binary()</v>
<v>IVec = binary()</v>
</type>
<desc>
<p>Returns the <c>IVec</c> to be used in a next iteration of
<c>aes_cbc_*_[encrypt|decrypt]</c>. <c>Data</c> is the encrypted
data from the previous iteration step.</p>
</desc>
</func>
<func>
<name>erlint(Mpint) -> N</name>
<name>mpint(N) -> Mpint</name>
<fsummary>Convert between binary multi-precision integer and erlang big integer</fsummary>
<type>
<v>Mpint = binary()</v>
<v>N = integer()</v>
</type>
<desc>
<p>Convert a binary multi-precision integer <c>Mpint</c> to and from
an erlang big integer. A multi-precision integer is a binary
with the following form:
<c><![CDATA[<<ByteLen:32/integer, Bytes:ByteLen/binary>>]]></c> where both
<c>ByteLen</c> and <c>Bytes</c> are big-endian. Mpints are used in
some of the functions in <c>crypto</c> and are not translated
in the API for performance reasons.</p>
</desc>
</func>
<func>
<name>rand_bytes(N) -> binary()</name>
<fsummary>Generate a binary of random bytes</fsummary>
<type>
<v>N = integer()</v>
</type>
<desc>
<p>Generates N bytes randomly uniform 0..255, and returns the
result in a binary. Uses the <c>crypto</c> library pseudo-random
number generator.</p>
</desc>
</func>
<func>
<name>rand_uniform(Lo, Hi) -> N</name>
<fsummary>Generate a random number</fsummary>
<type>
<v>Lo, Hi, N = Mpint | integer()</v>
<v>Mpint = binary()</v>
</type>
<desc>
<p>Generate a random number <c><![CDATA[N, Lo =< N < Hi.]]></c> Uses the
<c>crypto</c> library pseudo-random number generator. The
arguments (and result) can be either erlang integers or binary
multi-precision integers.</p>
</desc>
</func>
<func>
<name>mod_exp(N, P, M) -> Result</name>
<fsummary>Perform N ^ P mod M</fsummary>
<type>
<v>N, P, M, Result = Mpint</v>
<v>Mpint = binary()</v>
</type>
<desc>
<p>This function performs the exponentiation <c>N ^ P mod M</c>,
using the <c>crypto</c> library.</p>
</desc>
</func>
<func>
<name>rsa_sign(Data, Key) -> Signature</name>
<name>rsa_sign(DigestType, Data, Key) -> Signature</name>
<fsummary>Sign the data using rsa with the given key.</fsummary>
<type>
<v>Data = Mpint</v>
<v>Key = [E, N, D]</v>
<v>E, N, D = Mpint</v>
<d>Where <c>E</c> is the public exponent, <c>N</c> is public modulus and
<c>D</c> is the private exponent.</d>
<v>DigestType = md5 | sha</v>
<d>The default <c>DigestType</c> is sha.</d>
<v>Mpint = binary()</v>
<v>Signature = binary()</v>
</type>
<desc>
<p>Calculates a <c>DigestType</c> digest of the <c>Data</c>
and creates a RSA signature with the private key <c>Key</c>
of the digest.</p>
</desc>
</func>
<func>
<name>rsa_verify(Data, Signature, Key) -> Verified</name>
<name>rsa_verify(DigestType, Data, Signature, Key) -> Verified </name>
<fsummary>Verify the digest and signature using rsa with given public key.</fsummary>
<type>
<v>Verified = boolean()</v>
<v>Data, Signature = Mpint</v>
<v>Key = [E, N]</v>
<v>E, N = Mpint</v>
<d>Where <c>E</c> is the public exponent and <c>N</c> is public modulus.</d>
<v>DigestType = md5 | sha</v>
<d> The default <c>DigestType</c> is sha.</d>
<v>Mpint = binary()</v>
</type>
<desc>
<p>Calculates a <c>DigestType</c> digest of the <c>Data</c>
and verifies that the digest matches the RSA signature using the
signer's public key <c>Key</c>.
</p>
</desc>
</func>
<func>
<name>rsa_public_encrypt(PlainText, PublicKey, Padding) -> ChipherText</name>
<fsummary>Encrypts Msg using the public Key.</fsummary>
<type>
<v>PlainText = binary()</v>
<v>PublicKey = [E, N]</v>
<v>E, N = Mpint</v>
<d>Where <c>E</c> is the public exponent and <c>N</c> is public modulus.</d>
<v>Padding = rsa_pkcs1_padding | rsa_pkcs1_oaep_padding | rsa_no_padding</v>
<v>ChipherText = binary()</v>
</type>
<desc>
<p>Encrypts the <c>PlainText</c> (usually a session key) using the <c>PublicKey</c>
and returns the cipher. The <c>Padding</c> decides what padding mode is used,
<c>rsa_pkcs1_padding</c> is PKCS #1 v1.5 currently the most
used mode and <c>rsa_pkcs1_oaep_padding</c> is EME-OAEP as
defined in PKCS #1 v2.0 with SHA-1, MGF1 and an empty encoding
parameter. This mode is recommended for all new applications.
The size of the <c>Msg</c> must be less
than <c>byte_size(N)-11</c> if
<c>rsa_pkcs1_padding</c> is used, <c>byte_size(N)-41</c> if
<c>rsa_pkcs1_oaep_padding</c> is used and <c>byte_size(N)</c> if <c>rsa_no_padding</c>
is used.
Where byte_size(N) is the size part of an <c>Mpint-1</c>.
</p>
</desc>
</func>
<func>
<name>rsa_private_decrypt(ChipherText, PrivateKey, Padding) -> PlainText</name>
<fsummary>Decrypts ChipherText using the private Key.</fsummary>
<type>
<v>ChipherText = binary()</v>
<v>PrivateKey = [E, N, D]</v>
<v>E, N, D = Mpint</v>
<d>Where <c>E</c> is the public exponent, <c>N</c> is public modulus and
<c>D</c> is the private exponent.</d>
<v>Padding = rsa_pkcs1_padding | rsa_pkcs1_oaep_padding | rsa_no_padding</v>
<v>PlainText = binary()</v>
</type>
<desc>
<p>Decrypts the <c>ChipherText</c> (usually a session key encrypted with
<seealso marker="#rsa_public_encrypt/3">rsa_public_encrypt/3</seealso>)
using the <c>PrivateKey</c> and returns the
message. The <c>Padding</c> is the padding mode that was
used to encrypt the data,
see <seealso marker="#rsa_public_encrypt/3">rsa_public_encrypt/3</seealso>.
</p>
</desc>
</func>
<func>
<name>rsa_private_encrypt(PlainText, PrivateKey, Padding) -> ChipherText</name>
<fsummary>Encrypts Msg using the private Key.</fsummary>
<type>
<v>PlainText = binary()</v>
<v>PrivateKey = [E, N, D]</v>
<v>E, N, D = Mpint</v>
<d>Where <c>E</c> is the public exponent, <c>N</c> is public modulus and
<c>D</c> is the private exponent.</d>
<v>Padding = rsa_pkcs1_padding | rsa_no_padding</v>
<v>ChipherText = binary()</v>
</type>
<desc>
<p>Encrypts the <c>PlainText</c> using the <c>PrivateKey</c>
and returns the cipher. The <c>Padding</c> decides what padding mode is used,
<c>rsa_pkcs1_padding</c> is PKCS #1 v1.5 currently the most
used mode.
The size of the <c>Msg</c> must be less than <c>byte_size(N)-11</c> if
<c>rsa_pkcs1_padding</c> is used, and <c>byte_size(N)</c> if <c>rsa_no_padding</c>
is used. Where byte_size(N) is the size part of an <c>Mpint-1</c>.
</p>
</desc>
</func>
<func>
<name>rsa_public_decrypt(ChipherText, PublicKey, Padding) -> PlainText</name>
<fsummary>Decrypts ChipherText using the public Key.</fsummary>
<type>
<v>ChipherText = binary()</v>
<v>PublicKey = [E, N]</v>
<v>E, N = Mpint</v>
<d>Where <c>E</c> is the public exponent and <c>N</c> is public modulus</d>
<v>Padding = rsa_pkcs1_padding | rsa_no_padding</v>
<v>PlainText = binary()</v>
</type>
<desc>
<p>Decrypts the <c>ChipherText</c> (encrypted with
<seealso marker="#rsa_private_encrypt/3">rsa_private_encrypt/3</seealso>)
using the <c>PrivateKey</c> and returns the
message. The <c>Padding</c> is the padding mode that was
used to encrypt the data,
see <seealso marker="#rsa_private_encrypt/3">rsa_private_encrypt/3</seealso>.
</p>
</desc>
</func>
<func>
<name>dss_sign(Data, Key) -> Signature</name>
<fsummary>Sign the data using dsa with given private key.</fsummary>
<type>
<v>Digest = Mpint</v>
<v>Key = [P, Q, G, X]</v>
<v>P, Q, G, X = Mpint</v>
<d> Where <c>P</c>, <c>Q</c> and <c>G</c> are the dss
parameters and <c>X</c> is the private key.</d>
<v>Mpint = binary()</v>
<v>Signature = binary()</v>
</type>
<desc>
<p>Calculates the sha digest of the <c>Data</c>
and creates a DSS signature with the private key <c>Key</c>
of the digest.</p>
</desc>
</func>
<func>
<name>dss_verify(Data, Signature, Key) -> Verified</name>
<fsummary>Verify the data and signature using dsa with given public key.</fsummary>
<type>
<v>Verified = boolean()</v>
<v>Digest, Signature = Mpint</v>
<v>Key = [P, Q, G, Y]</v>
<v>P, Q, G, Y = Mpint</v>
<d> Where <c>P</c>, <c>Q</c> and <c>G</c> are the dss
parameters and <c>Y</c> is the public key.</d>
<v>Mpint = binary()</v>
</type>
<desc>
<p>Calculates the sha digest of the <c>Data</c> and verifies that the
digest matches the DSS signature using the public key <c>Key</c>.
</p>
</desc>
</func>
<func>
<name>rc4_encrypt(Key, Data) -> Result</name>
<fsummary>Encrypt data using RC4</fsummary>
<type>
<v>Key, Data = iolist() | binary()</v>
<v>Result = binary()</v>
</type>
<desc>
<p>Encrypts the data with RC4 symmetric stream encryption.
Since it is symmetric, the same function is used for
decryption.</p>
</desc>
</func>
<func>
<name>dh_generate_key(DHParams) -> {PublicKey,PrivateKey} </name>
<name>dh_generate_key(PrivateKey, DHParams) -> {PublicKey,PrivateKey} </name>
<fsummary>Generates a Diffie-Hellman public key</fsummary>
<type>
<v>DHParameters = [P, G]</v>
<v>P, G = Mpint</v>
<d> Where <c>P</c> is the shared prime number and <c>G</c> is the shared generator.</d>
<v>PublicKey, PrivateKey = Mpint()</v>
</type>
<desc>
<p>Generates a Diffie-Hellman <c>PublicKey</c> and <c>PrivateKey</c> (if not given).
</p>
</desc>
</func>
<func>
<name>dh_compute_key(OthersPublicKey, MyPrivateKey, DHParams) -> SharedSecret</name>
<fsummary>Computes the shared secret</fsummary>
<type>
<v>DHParameters = [P, G]</v>
<v>P, G = Mpint</v>
<d> Where <c>P</c> is the shared prime number and <c>G</c> is the shared generator.</d>
<v>OthersPublicKey, MyPrivateKey = Mpint()</v>
<v>SharedSecret = binary()</v>
</type>
<desc>
<p>Computes the shared secret from the private key and the other party's public key.
</p>
</desc>
</func>
<func>
<name>exor(Data1, Data2) -> Result</name>
<fsummary>XOR data</fsummary>
<type>
<v>Data1, Data2 = iolist() | binary()</v>
<v>Result = binary()</v>
</type>
<desc>
<p>Performs bit-wise XOR (exclusive or) on the data supplied.</p>
</desc>
</func>
</funcs>
<section>
<title>DES in CBC mode</title>
<p>The Data Encryption Standard (DES) defines an algorithm for
encrypting and decrypting an 8 byte quantity using an 8 byte key
(actually only 56 bits of the key is used).
</p>
<p>When it comes to encrypting and decrypting blocks that are
multiples of 8 bytes various modes are defined (NIST SP
800-38A). One of those modes is the Cipher Block Chaining (CBC)
mode, where the encryption of an 8 byte segment depend not only
of the contents of the segment itself, but also on the result of
encrypting the previous segment: the encryption of the previous
segment becomes the initializing vector of the encryption of the
current segment.
</p>
<p>Thus the encryption of every segment depends on the encryption
key (which is secret) and the encryption of the previous
segment, except the first segment which has to be provided with
an initial initializing vector. That vector could be chosen at
random, or be a counter of some kind. It does not have to be
secret.
</p>
<p>The following example is drawn from the old FIPS 81 standard
(replaced by NIST SP 800-38A), where both the plain text and the
resulting cipher text is settled. The following code fragment
returns `true'.
</p>
<pre><![CDATA[
Key = <<16#01,16#23,16#45,16#67,16#89,16#ab,16#cd,16#ef>>,
IVec = <<16#12,16#34,16#56,16#78,16#90,16#ab,16#cd,16#ef>>,
P = "Now is the time for all ",
C = crypto:des_cbc_encrypt(Key, IVec, P),
% Which is the same as
P1 = "Now is t", P2 = "he time ", P3 = "for all ",
C1 = crypto:des_cbc_encrypt(Key, IVec, P1),
C2 = crypto:des_cbc_encrypt(Key, C1, P2),
C3 = crypto:des_cbc_encrypt(Key, C2, P3),
C = <<C1/binary, C2/binary, C3/binary>>,
C = <<16#e5,16#c7,16#cd,16#de,16#87,16#2b,16#f2,16#7c,
16#43,16#e9,16#34,16#00,16#8c,16#38,16#9c,16#0f,
16#68,16#37,16#88,16#49,16#9a,16#7c,16#05,16#f6>>,
<<"Now is the time for all ">> ==
crypto:des_cbc_decrypt(Key, IVec, C).
]]></pre>
<p>The following is true for the DES CBC mode. For all
decompositions <c>P1 ++ P2 = P</c> of a plain text message
<c>P</c> (where the length of all quantities are multiples of 8
bytes), the encryption <c>C</c> of <c>P</c> is equal to <c>C1 ++
C2</c>, where <c>C1</c> is obtained by encrypting <c>P1</c> with
<c>Key</c> and the initializing vector <c>IVec</c>, and where
<c>C2</c> is obtained by encrypting <c>P2</c> with <c>Key</c>
and the initializing vector <c>last8(C1)</c>,
where <c>last(Binary)</c> denotes the last 8 bytes of the
binary <c>Binary</c>.
</p>
<p>Similarly, for all decompositions <c>C1 ++ C2 = C</c> of a
cipher text message <c>C</c> (where the length of all quantities
are multiples of 8 bytes), the decryption <c>P</c> of <c>C</c>
is equal to <c>P1 ++ P2</c>, where <c>P1</c> is obtained by
decrypting <c>C1</c> with <c>Key</c> and the initializing vector
<c>IVec</c>, and where <c>P2</c> is obtained by decrypting
<c>C2</c> with <c>Key</c> and the initializing vector
<c>last8(C1)</c>, where <c>last8(Binary)</c> is as above.
</p>
<p>For DES3 (which uses three 64 bit keys) the situation is the
same.
</p>
</section>
</erlref>
