Refer to EVP_DigestInit() in the hash function descriptions.

B<r> (C<r=a/2^n>). BN_rshift1() shifts B<a> right by one and places

the result in B<r> (C<r=a/2>).

For the shift functions, B<r> and B<a> may be the same variable.

=head1 RETURN VALUES

BN_is_bit_set() returns 1 if the bit is set, 0 otherwise.

The EVP digest routines are a high level interface to message digests.

B<EVP_DigestInit()> initialises a digest context B<ctx> to use a digest

EVP_DigestInit() initialises a digest context B<ctx> to use a digest

B<type>: this will typically be supplied by a function such as

B<EVP_sha1()>.

EVP_sha1().

B<EVP_DigestUpdate()> hashes B<cnt> bytes of data at B<d> into the

EVP_DigestUpdate() hashes B<cnt> bytes of data at B<d> into the

digest context B<ctx>. This funtion can be called several times on the

same B<ctx> to hash additional data.

B<EVP_DigestFinal()> retrieves the digest value from B<ctx> and places

EVP_DigestFinal() retrieves the digest value from B<ctx> and places

it in B<md>. If the B<s> parameter is not NULL then the number of

bytes of data written (i.e. the length of the digest) will be written

to the integer at B<s>, at most B<EVP_MAX_MD_SIZE> bytes will be written.

After calling B<EVP_DigestFinal> no additional calls to B<EVP_DigestUpdate>

can be made, but B<EVP_DigestInit> can be called to initialiase a new

After calling EVP_DigestFinal() no additional calls to EVP_DigestUpdate()

can be made, but EVP_DigestInit() can be called to initialiase a new

digest operation.

B<EVP_MD_CTX_copy> can be used to copy the message digest state from

EVP_MD_CTX_copy() can be used to copy the message digest state from

B<in> to B<out>. This is useful if large amounts of data are to be

hashed which only differ in the last few bytes.

B<EVP_MD_size> and B<EVP_MD_CTX_size> return the size of the message digest

EVP_MD_size() and EVP_MD_CTX_size() return the size of the message digest

when passed an B<EVP_MD> or an B<EVP_MD_CTX> structure, i.e. the size of the

hash.

B<EVP_MD_block_size> and B<EVP_MD_CTX_block_size> return the block size of the

EVP_MD_block_size() and EVP_MD_CTX_block_size() return the block size of the

message digest when passed an B<EVP_MD> or an B<EVP_MD_CTX> structure.

B<EVP_MD_type> and B<EVP_MD_CTX_type> return the NID of the OBJECT IDENTIFIER

EVP_MD_type() and EVP_MD_CTX_type() return the NID of the OBJECT IDENTIFIER

representing the given message digest when passed an B<EVP_MD> structure.

For example B<EVP_MD_type(EVP_sha1())> returns B<NID_sha1>. This function is

For example EVP_MD_type(EVP_sha1()) returns B<NID_sha1>. This function is

normally used when setting ASN1 OIDs.

B<EVP_MD_CTX_type> return the B<EVP_MD> structure corresponding to the passed

EVP_MD_CTX_type() returns the B<EVP_MD> structure corresponding to the passed

B<EVP_MD_CTX>.

B<EVP_MD_pkey_type> returns the NID of the public key signing algorithm associated

with this digest. For example B<EVP_sha1()> is associated with RSA so this will

EVP_MD_pkey_type() returns the NID of the public key signing algorithm associated

with this digest. For example EVP_sha1() is associated with RSA so this will

return B<NID_sha1WithRSAEncryption>. This "link" between digests and signature

algorithms may not be retained in future versions of OpenSSL.

B<EVP_md2>, B<EVP_md5>, B<EVP_sha>, B<EVP_sha1>, B<EVP_mdc2> and B<EVP_ripemd160>

EVP_md2(), EVP_md5(), EVP_sha(), EVP_sha1(), EVP_mdc2() and EVP_ripemd160()

return B<EVP_MD> structures for the MD2, MD5, SHA, SHA1, MDC2 and RIPEMD160 digest

algorithms respectively. The associated signature algorithm is RSA in each case.

B<EVP_dss> and B<EVP_dss1> return B<EVP_MD> structures for SHA and SHA1 digest

EVP_dss() and EVP_dss1() return B<EVP_MD> structures for SHA and SHA1 digest

algorithms but using DSS (DSA) for the signature algorithm.

B<EVP_md_null> is a "null" message digest that does nothing: i.e. the hash it

EVP_md_null() is a "null" message digest that does nothing: i.e. the hash it

returns is of zero length.

B<EVP_get_digestbyname>, B<EVP_get_digestbynid> and B<EVP_get_digestbyobj>

EVP_get_digestbyname(), EVP_get_digestbynid() and EVP_get_digestbyobj()

return an B<EVP_MD> structure when passed a digest name, a digest NID or

and ASN1_OBJECT structure respectively. The digest table must be initialised

using, for example, B<OpenSSL_add_all_digests()> for these functions to work.

using, for example, OpenSSL_add_all_digests() for these functions to work.

=head1 RETURN VALUES

might.

The link between digests and signing algorithms results in a situation where

B<EVP_sha1()> must be used with RSA and B<EVP_dss1()> must be used with DSS

EVP_sha1() must be used with RSA and EVP_dss1() must be used with DSS

even though they are identical digests.

The size of an B<EVP_MD_CTX> structure is determined at compile time: this results

=head1 SEE ALSO

L<evp(3)|evp(3)>, L<hmac(3)|hmac(3)>, L<md2(3)|md2(3)>,

L<md5(3)|md5(3)>, L<mdc2(3)|mdc2(3)>, L<ripemd(3)|ripemd(3)>,

L<sha(3)|sha(3)>

=head1 HISTORY

EVP_DigestInit(), EVP_DigestUpdate() and EVP_DigestFinal() are

available in all versions of SSLeay and OpenSSL.

=cut

MD5_Init(), MD5_Update() and MD5_Final() are analogous using an

B<MD5_CTX> structure.

Applications should use the higher level functions EVP_DigestInit(3) etc.

instead of calling the hash functions directly.

=head1 NOTE

MD2 and MD5 are recommended only for compatibility with existing

=head1 SEE ALSO

L<sha(3)|sha(3)>, L<ripemd(3)|ripemd(3)>

L<sha(3)|sha(3)>, L<ripemd(3)|ripemd(3)>, L<EVP_DigestInit(3)|EVP_DigestInit(3)>

=head1 HISTORY

MDC2_Init(), MDC2_Update() and MDC2_Final() do not return values.

Applications should use the higher level functions EVP_DigestInit(3) etc.

instead of calling the hash functions directly.

=head1 CONFORMING TO

ISO/IEC 10118-2, with DES

=head1 SEE ALSO

L<sha(3)|sha(3)>

L<sha(3)|sha(3)>, L<EVP_DigestInit(3)|EVP_DigestInit(3)>

=head1 HISTORY

space for RIPEMD160_DIGEST_LENGTH == 20 bytes of output, and erases

the B<RIPEMD160_CTX>.

Applications should use the higher level functions EVP_DigestInit(3) etc.

instead of calling the hash functions directly.

=head1 RETURN VALUES

RIPEMD160() returns a pointer to the hash value. 

=head1 SEE ALSO

L<sha(3)|sha(3)>, L<hmac(3)|hmac(3)>

L<sha(3)|sha(3)>, L<hmac(3)|hmac(3)>, L<EVP_DigestInit(3)|EVP_DigestInit(3)>

=head1 HISTORY