May 26, 2017 GPG, or GNU Privacy Guard, is a public key cryptography implementation. This allows for the secure transmission of information between parties and can be used to verify that the origin of a message is genuine. In this guide, we will discuss how GPG works and how to implement it.
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4.5.4 Unattended key generation
The command --generate-key may be used along with the option--batch for unattended key generation. This is the mostflexible way of generating keys, but it is also the most complex one.Consider using the quick key manipulation interface described in theprevious subsection “The quick key manipulation interface”.
The parameters for the key are either read from stdin or given as afile on the command line. The format of the parameter file is asfollows:
- Nov 24, 2013 Generating More Secure GPG Keys: A Step-by-Step Guide (this post) Using an OpenPGP Smartcard with GnuPG In this post, I’ll will cover the generation of a new GPG key and removal of the primary key, one of two mitigation strategies mentioned in the previous post.
- GnuPG is a complete and free implementation of the OpenPGP standard as defined by RFC4880 (also known as PGP).GnuPG allows you to encrypt and sign your data and communications; it features a versatile key management system, along with access modules for all kinds of public key directories.
- Text only, line length is limited to about 1000 characters.
- UTF-8 encoding must be used to specify non-ASCII characters.
- Empty lines are ignored.
- Leading and trailing white space is ignored.
- A hash sign as the first non white space character indicates a comment line.
- Control statements are indicated by a leading percent sign, the arguments are separated by white space from the keyword.
- Parameters are specified by a keyword, followed by a colon. Arguments are separated by white space.
- The first parameter must be ‘Key-Type’; control statements may be placed anywhere.
- The order of the parameters does not matter except for ‘Key-Type’ which must be the first parameter. The parameters are only used for the generated keyblock (primary and subkeys); parameters from previous sets are not used. Some syntactically checks may be performed.
- Key generation takes place when either the end of the parameter file is reached, the next ‘Key-Type’ parameter is encountered or at the control statement ‘%commit’ is encountered.
Control statements:
Print text as diagnostic.
Suppress actual key generation (useful for syntax checking).
Perform the key generation. Note that an implicit commit is done atthe next Key-Type parameter.
Do not write the key to the default or commandline given keyring butto filename. This must be given before the first commit to takeplace, duplicate specification of the same filename is ignored, thelast filename before a commit is used. The filename is used until anew filename is used (at commit points) and all keys are written tothat file. If a new filename is given, this file is created (andoverwrites an existing one).
See the previous subsection “Ephemeral home directories” for a morerobust way to contain side-effects.
This option is a no-op for GnuPG 2.1 and later.
See the previous subsection “Ephemeral home directories”.
This option is a no-op for GnuPG 2.1 and later.
Using this option allows the creation of keys without any passphraseprotection. This option is mainly intended for regression tests.
If given the keys are created using a faster and a somewhat lesssecure random number generator. This option may be used for keyswhich are only used for a short time and do not require fullcryptographic strength. It takes only effect if used together withthe control statement ‘%no-protection’.
General Parameters:
Starts a new parameter block by giving the type of the primarykey. The algorithm must be capable of signing. This is a requiredparameter. algo may either be an OpenPGP algorithm number or astring with the algorithm name. The special value ‘default’ maybe used for algo to create the default key type; in this case a‘Key-Usage’ shall not be given and ‘default’ also be usedfor ‘Subkey-Type’.
The requested length of the generated key in bits. The default isreturned by running the command ‘gpg --gpgconf-list’.
Gpg Import Secret Key
Gpg Keyserver List
This is optional and used to generate a CSR or certificate for analready existing key. Key-Length will be ignored when given.
Space or comma delimited list of key usages. Allowed values are‘encrypt’, ‘sign’, and ‘auth’. This is used togenerate the key flags. Please make sure that the algorithm iscapable of this usage. Note that OpenPGP requires that all primarykeys are capable of certification, so no matter what usage is givenhere, the ‘cert’ flag will be on. If no ‘Key-Usage’ isspecified and the ‘Key-Type’ is not ‘default’, all allowedusages for that particular algorithm are used; if it is not given but‘default’ is used the usage will be ‘sign’.
This generates a secondary key (subkey). Currently only one subkeycan be handled. See also ‘Key-Type’ above.
Length of the secondary key (subkey) in bits. The default is returnedby running the command ‘gpg --gpgconf-list’.
Key usage lists for a subkey; similar to ‘Key-Usage’.
If you want to specify a passphrase for the secret key, enter it here.Default is to use the Pinentry dialog to ask for a passphrase.
The three parts of a user name. Remember to use UTF-8 encoding here.If you don’t give any of them, no user ID is created.
Set the expiration date for the key (and the subkey). It may eitherbe entered in ISO date format (e.g. '20000815T145012') or as number ofdays, weeks, month or years after the creation date. The specialnotation 'seconds=N' is also allowed to specify a number of secondssince creation. Without a letter days are assumed. Note that thereis no check done on the overflow of the type used by OpenPGP fortimestamps. Thus you better make sure that the given value makesense. Although OpenPGP works with time intervals, GnuPG uses anabsolute value internally and thus the last year we can represent is2105.
Set the creation date of the key as stored in the key information andwhich is also part of the fingerprint calculation. Either a date like'1986-04-26' or a full timestamp like '19860426T042640' may be used.The time is considered to be UTC. The special notation 'seconds=N'may be used to directly specify a the number of seconds since Epoch(Unix time). If it is not given the current time is used.
Set the cipher, hash, and compression preference values for this key.This expects the same type of string as the sub-command ‘setpref’in the --edit-key menu.
Add a designated revoker to the generated key. Algo is the public keyalgorithm of the designated revoker (i.e. RSA=1, DSA=17, etc.)fpr is the fingerprint of the designated revoker. The optional‘sensitive’ flag marks the designated revoker as sensitiveinformation. Only v4 keys may be designated revokers.
Gpg Export Secret Key
This is an optional parameter that specifies the preferred keyserverURL for the key.
This is an optional parameter only used with the status linesKEY_CREATED and KEY_NOT_CREATED. string may be up to 100characters and should not contain spaces. It is useful for batch keygeneration to associate a key parameter block with a status line.
Here is an example on how to create a key in an ephemeral home directory:
If you want to create a key with the default algorithms you would usethese parameters:
Gpg Export Private Key
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