The signature calculation is based on a hash of the signed data, as
described above. The details of the calculation are different for DSA
signatures than for RSA signatures.¶

With RSA signatures, the hash value is encoded using PKCS#1 encoding
type EMSA-PKCS1-v1_5 as described in Section 9.2 of RFC 3447. This
requires inserting the hash value as an octet string into an ASN.1
structure. The object identifier for the type of hash being used is
included in the structure. The hexadecimal representations for the
currently defined hash algorithms are as follows:¶

- MD5: 0x2A, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x02, 0x05
- RIPEMD-160: 0x2B, 0x24, 0x03, 0x02, 0x01
- SHA-1: 0x2B, 0x0E, 0x03, 0x02, 0x1A
- SHA2-224: 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x04
- SHA2-256: 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x01
- SHA2-384: 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x02
- SHA2-512: 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x03

¶
- MD5: 1.2.840.113549.2.5
- RIPEMD-160: 1.3.36.3.2.1
- SHA-1: 1.3.14.3.2.26
- SHA2-224: 2.16.840.1.101.3.4.2.4
- SHA2-256: 2.16.840.1.101.3.4.2.1
- SHA2-384: 2.16.840.1.101.3.4.2.2
- SHA2-512: 2.16.840.1.101.3.4.2.3

¶
- MD5: 0x30, 0x20, 0x30, 0x0C, 0x06, 0x08, 0x2A, 0x86,
0x48, 0x86, 0xF7, 0x0D, 0x02, 0x05, 0x05, 0x00,
0x04, 0x10
- RIPEMD-160: 0x30, 0x21, 0x30, 0x09, 0x06, 0x05, 0x2B, 0x24,
0x03, 0x02, 0x01, 0x05, 0x00, 0x04, 0x14
- SHA-1: 0x30, 0x21, 0x30, 0x09, 0x06, 0x05, 0x2b, 0x0E,
0x03, 0x02, 0x1A, 0x05, 0x00, 0x04, 0x14
- SHA2-224: 0x30, 0x2D, 0x30, 0x0d, 0x06, 0x09, 0x60, 0x86,
0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x04, 0x05,
0x00, 0x04, 0x1C
- SHA2-256: 0x30, 0x31, 0x30, 0x0d, 0x06, 0x09, 0x60, 0x86,
0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x01, 0x05,
0x00, 0x04, 0x20
- SHA2-384: 0x30, 0x41, 0x30, 0x0d, 0x06, 0x09, 0x60, 0x86,
0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x02, 0x05,
0x00, 0x04, 0x30
- SHA2-512: 0x30, 0x51, 0x30, 0x0d, 0x06, 0x09, 0x60, 0x86,
0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x03, 0x05,
0x00, 0x04, 0x40

¶
DSA signatures MUST use hashes that are equal in size to the number of
bits of q, the group generated by the DSA key's generator value.¶

If the output size of the chosen hash is larger than the number of
bits of q, the hash result is truncated to fit by taking the number of
leftmost bits equal to the number of bits of q. This (possibly
truncated) hash function result is treated as a number and used
directly in the DSA signature algorithm.¶