|-c||print out the digest in two digit groups separated by colons, only relevant if hex format output is used.|
|-d||print out BIO debugging information.|
|-hex||digest is to be output as a hex dump. This is the default case for a normal digest as opposed to a digital signature. See NOTES below for digital signatures using -hex.|
|-binary||output the digest or signature in binary form.|
|-r||output the digest in the coreutils format used by programs like sha1sum.|
|-non-fips-allow||Allow use of non FIPS digest when in FIPS mode. This has no effect when not in FIPS mode.|
|-out filename||filename to output to, or standard output by default.|
|-sign filename||digitally sign the digest using the private key in filename.|
|-keyform arg||Specifies the key format to sign digest with. The DER, PEM, P12, and ENGINE formats are supported.|
|-engine id||Use engine id for operations (including private key storage). This engine is not used as source for digest algorithms, unless it is also specified in the configuration file.|
|-sigopt nm:v||Pass options to the signature algorithm during sign or verify operations. Names and values of these options are algorithm-specific.|
|-passin arg||the private key password source. For more information about the format of arg see the PASS PHRASE ARGUMENTS section in openssl(1).|
|-verify filename||verify the signature using the public key in filename. The output is either Verification OK or Verification Failure.|
|-prverify filename||verify the signature using the private key in filename.|
|-signature filename||the actual signature to verify.|
|-hmac key||create a hashed MAC using key.|
|-mac alg||create MAC (keyed Message Authentication Code). The most popular MAC algorithm is HMAC (hash-based MAC), but there are other MAC algorithms which are not based on hash, for instance gost-mac algorithm, supported by ccgost engine. MAC keys and other options should be set via -macopt parameter.|
Passes options to MAC algorithm, specified by -mac key.
Following options are supported by both by HMAC and gost-mac:
|-rand file(s)||a file or files containing random data used to seed the random number generator, or an EGD socket (see RAND_egd(3)). Multiple files can be specified separated by a OS-dependent character. The separator is ; for MS-Windows, , for OpenVMS, and : for all others.|
|-non-fips-allow||enable use of non-FIPS algorithms such as MD5 even in FIPS mode.|
|-fips-fingerprint||compute HMAC using a specific key for certain OpenSSL-FIPS operations.|
|file...||file or files to digest. If no files are specified then standard input is used.|
To create a hex-encoded message digest of a file:
openssl dgst -md5 -hex file.txt
To sign a file using SHA-256 with binary file output:
openssl dgst -sha256 -sign privatekey.pem -out signature.sign file.txt
To verify a signature:
openssl dgst -sha256 -verify publickey.pem \
-signature signature.sign \
The digest of choice for all new applications is SHA1. Other digests are however still widely used.
When signing a file, dgst will automatically determine the algorithm (RSA, ECC, etc) to use for signing based on the private keys ASN.1 info. When verifying signatures, it only handles the RSA, DSA, or ECDSA signature itself, not the related data to identify the signer and algorithm used in formats such as x.509, CMS, and S/MIME.
A source of random numbers is required for certain signing algorithms, in particular ECDSA and DSA.
The signing and verify options should only be used if a single file is being signed or verified.
Hex signatures cannot be verified using openssl. Instead, use xxd -r or similar program to transform the hex signature into a binary signature prior to verification.