I also read the man page and didn't find a hint what I might miss or did wrong. Also please be aware that I know that passing the password to gpg that way isn't the most secure way ;. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. GPG large file decryption duration Ask Question. Asked 1 year, 10 months ago. Active 1 year, 10 months ago.
Viewed 2k times. Improve this question. Monarch Monarch 11 4 4 bronze badges. Make sure to use gpg 2. See this question: security. Robert Thank you for your answer. I updated my Question with my current system specs. Anyone who trusts the CA will automatically consider any certificates signed by the CA to be valid. Another aspect of checking validity is to ensure that the certificate has not been revoked. For more information, see the section Certificate Revocation.
Meta and trusted introducers In most situations, people completely trust the CA to establish certificates' validity. This means that everyone else relies upon the CA to go through the whole manual validation process for them. This is fine up to a certain number of users or number of work sites, and then it is not possible for the CA to maintain the same level of quality validation.
In that case, adding other validators to the system is necessary. A CA can also be a meta- introducer. A meta-introducer bestows not only validity on keys, but bestows the ability to trust keys upon others. Similar to the king who hands his seal to his trusted advisors so they can act on his authority, the meta-introducer enables others to act as trusted introducers.
These trusted introducers can validate keys to the same effect as that of the meta-introducer. They cannot, however, create new trusted introducers. Meta-introducer and trusted introducer are PGP terms. In an X. The root CA uses the private key associated with a special certificate type called a root CA certificate to sign certificates. Any certificate signed by the root CA certificate is viewed as valid by any other certificate signed by the root. This validation process works even for certificates signed by other CAs in the system — as long as the root CA certificate signed the subordinate CA's certificate, any certificate signed by the CAis considered valid to others within the hierarchy.
This process of checking back up through the systemto see who signed whose certificate is called tracing a certification path or certification chain. Companies followone or another trust model, which dictates how users will go about establishing certificate validity.
There are three different models:. In PGP, a user who validates keys herself and never sets another certificate to be a trusted introducer is using direct trust. Direct trust. Hierarchical Trust In a hierarchical system, there are a number of "root" certificates from which trust extends. These certificates may certify certificates themselves, or they may certify certificates that certify still other certificates down some chain.
Consider it as a big trust "tree. Hierarchical trust. Web of Trust A web of trust encompasses both of the other models, but also adds the notion that trust is in the eye of the beholder which is the real-world view and the idea that more information is better. It is thus a cumulative trust model.
A certificate might be trusted directly, or trusted in some chain going back to a directly trusted root certificate the meta-introducer , or by some group of introducers. Perhaps you've heard of the term six degrees of separation, which suggests that any person in the world can determine some link to any other person in the world using six or fewer other people as intermediaries.
This is a web of introducers. It is also the PGP view of trust. PGP uses digital signatures as its form of introduction. When any user signs another's key, he or she becomes an introducer of that key. As this process goes on, it establishes a web of trust. In a PGP environment, any user can act as a certifying authority. However, such a certificate is only valid to another user if the relying party recognizes the validator as a trusted introducer.
That is, you trust my opinion that others' keys are valid only if you consider me to be a trusted introducer. Otherwise, my opinion on other keys' validity is moot. Stored on each user's public keyring are indicators of.
Levels of trust in PGP The highest level of trust in a key, implicit trust, is trust in your own key pair. PGP assumes that if you own the private key, you must trust the actions of its related public key.
Any keys signed by your implicitly trusted key are valid. There are three levels of trust you can assign to someone else's public key:. For example, suppose your key ring contains Alice's key. You have validated Alice's key and you indicate this by signing it. You know that Alice is a real stickler for validating others' keys. You therefore assign her key with Complete trust.
This makes Alice a Certification Authority. If Alice signs another's key, it appears as Valid on your keyring. PGP requires one Completely trusted signature or two Marginally trusted signatures to establish a key as valid.
You might consider Alice fairly trustworthy and also consider Bob fairly trustworthy. Either one alone runs the risk of accidentally signing a counterfeit key, so you might not place complete trust in either one. However, the odds that both individuals signed the same phony key are probably small.
The certificate is expected to be usable for its entire validity period its lifetime. The certificate can still be safely used to reconfirm information that was encrypted or signed within the validity period — it should not be trusted for cryptographic tasks moving forward, however. There are also situations where it is necessary to invalidate a certificate prior to its expiration date, such as when an the certificate holder terminates employment with the company or suspects that the certificate's corresponding private key has been compromised.
This is called revocation. Arevoked certificate is much more suspect than an expired certificate. Expired certificates are unusable, but do not carry the same threat of compromise as a revoked certificate. Anyone who has signed a certificate can revoke his or her signature on the certificate provided he or she uses the same private key that created the signature. Arevoked signature indicates that the signer no longer believes the public key and identification information belong together, or that the certificate's public key or corresponding private key has been compromised.
A revoked signature should carry nearly as much weight as a revoked certificate. PGP certificates provide the added feature that you can revoke your entire certificate not just the signatures on it if you yourself feel that the certificate has been compromised. Only the certificate's owner the holder of its corresponding private key or someone whom the certificate's owner has designated as a revoker can revoke a PGP certificate.
Designating a revoker is a useful practice, as it's often the loss of the passphrase for the certificate's corresponding private key that leads a PGP user to revoke his or her certificate — a task that is only possible if one has access to the private key. Only the certificate's issuer can revoke an X. The CRL contains a time-stamped, validated list of all revoked, unexpired certificates in the system.
Revoked certificates remain on the list only until they expire, then they are removed from the list — this keeps the list from getting too long. The CA distributes the CRL to users at some regularly scheduled interval and potentially off-cycle, whenever a certificate is revoked.
Theoretically, this will prevent users from unwittingly using a compromised certificate. It is possible, though, that there may be a time period between CRLs in which a newly compromised certificate is used. A passphrase is a longer version of a password, and in theory, a more secure one. Typically composed of multiple words, a passphrase is more secure against standard dictionary attacks, wherein the attacker tries all the words in the dictionary in an attempt to determine your password.
The best passphrases are relatively long and complex and contain a combination of upper and lowercase letters, numeric and punctuation characters. PGP uses a passphrase to encrypt your private key on your machine.
Your private key is encrypted on your disk using a hash of your passphrase as the secret key. You use the passphrase to decrypt and use your private key. A passphrase should be hard for you to forget and difficult for others to guess. It should be something already firmly embedded in your long-term memory, rather than something you make up from scratch. Because if you forget your passphrase, you are out of luck.
Your private key is totally and absolutely useless without your passphrase and nothing can be done about it. Remember the quote earlier in this chapter? PGP is cryptography that will keep major governments out of your files.
It will certainly keep you out of your files, too. Keep that in mind when you decide to change your passphrase to the punchline of that joke you can never quite remember.
Insucha caseit is wisetosplit the key among multiple people in such a way that more than one or two people must present a piece of the key in order to reconstitute it to a usable condition. If too few pieces of the key are available, then the key is unusable. Some examples are to split a key into three pieces and require two of them to reconstitute the key, or split it into two pieces and require both pieces.
If a secure network connection is used during the reconstitution process, the key's shareholders need not be physically present in order to rejoin the key. The Basics of Cryptography Encryption and decryption What is cryptography?
Strong cryptography How does cryptography work? Conventional cryptography Caesar's Cipher Key management and conventional encryption Public key cryptography How PGP works Keys Digital signatures Hash functions Digital certificates Certificate distribution Certificate formats Validity and trust Checking validity Establishing trust Trust models Certificate Revocation Communicating that a certificate has been revoked What is a passphrase? Key splitting The Basics of Cryptography When Julius Caesar sent messages to his generals, he didn't trust his messengers.
And so we begin. Encryption and decryption Data that can be read and understood without any special measures is called plaintext or cleartext. The method of disguising plaintext in such a way as to hide its substance is called encryption. Encrypting plaintext results in unreadable gibberish called ciphertext. You use encryption to ensure that information is hidden from anyone for whom it is not intended, even those who can see the encrypted data.
The process of reverting ciphertext to its original plaintext is called decryption. Figure illustrates this process. Encryption and decryption What is cryptography? Cryptography is the science of using mathematics to encrypt and decrypt data. Cryptography enables you to store sensitive information or transmit it across insecure networks like the Internet so that it cannot be read by anyone except the intended recipient.
Strong cryptography "There are two kinds of cryptography in this world: cryptography that will stop your kid sister from reading your files, and cryptography that will stop major governments from reading your files.
This book is about the latter. How does cryptography work? A cryptographic algorithm, or cipher, is a mathematical function used in the encryption and decryption process. A cryptographic algorithm works in combination with a key — a word, number, or phrase — to encrypt the plaintext. The same plaintext encrypts to different ciphertext with different keys. The security of encrypted data is entirely dependent on two things: the strength of the cryptographic algorithm and the secrecy of the key.
Conventional cryptography In conventional cryptography, also called secret-key or symmetric-key encryption, one key is used both for encryption and decryption.
Figure is an illustration of the conventional encryption process. Conventional encryption Caesar's Cipher An extremely simple example of conventional cryptography is a substitution cipher. A substitution cipher substitutes one piece of information for another. This is most frequently done by offsetting letters of the alphabet.
In both cases, the algorithm is to offset the alphabet and the key is the number of characters to offset it. Key management and conventional encryption Conventional encryption has benefits. It is very fast. It is especially useful for encrypting data that is not going anywhere. However, conventional encryption alone as a means for transmitting secure data can be quite expensive simply due to the difficulty of secure key distribution.
Public key cryptography The problems of key distribution are solved by public key cryptography, the concept of which was introduced by Whitfield Diffie and Martin Hellman in There is now evidence that the British Secret Service invented it a few years before Diffie and Hellman, but kept it a military secret — and did nothing with it. Today, the popularity of PGP has grown significantly. As more users have realized just how much information corporations and their governments are collecting on them, huge numbers of people now use the standard to keep their private information private.
A related use of PGP is that it can be used for email verification. If a journalist is unsure about the identity of a person sending them a message, for instance, they can use a Digital Signature alongside PGP to verify this. If even one character of the message has been changed in transit, the recipient will know. This can indicate either the sender is not who they say they are, that they have tried to fake a Digital Signature, or that the message has been tampered with.
A third use of PGP is to encrypt files. In fact, this algorithm is so secure that it has even been used in high-profile malware such as the CryptoLocker malware. This software offers PGP encryption for all your files, whilst also hiding the complexities of encryption and decryption processes.
Whether you need to use PGP encryption will depend on how secure you want your communications or files to be. As with any privacy or security software, using PGP requires that you do a little more work when sending and receiving messages, but can also dramatically improve the resilience of your systems to attack.
The major pro of PGP encryption is that it is essentially unbreakable. The biggest con of PGP encryption is that it is not that user-friendly. This is changing — thanks to off-the-shelf solutions that we will come to shortly — but using PGP can add significant extra work and time to your daily schedule. In addition, those using the system need to be aware of how it works, in case they introduce security holes by using it incorrectly.
This means that businesses considering a move to PGP will need to provide training. For that reason, many businesses might want to consider alternatives. There are encrypted messaging apps like Signal, for instance, that offer encryption that is more straightforward to use. In terms of storing data, anonymisation can be a good alternative to encryption and can be a more efficient use of resources.
Unlike anonymous browsers using proxy servers or working through a VPN to hide your true location, emails sent through PGP can be traced to a sender and recipient. In the vast majority of cases, setting up PGP encryption involves downloading an add-on for your email program, and then following the installation instructions. There are add-ons like this available for Thunderbird, Outlook, and Apple Mail, and we will describe these below. In recent years we have also seen the emergence of a number of online email systems that include PGP by default the most famous being ProtonMail.
For those of you looking to use PGP to encrypt your files, there are a number of large-scale software solutions available.
Symantec, for example, offers PGP-based products such as Symantec File Share Encryption for encrypting files shared across a network and Symantec Endpoint Encryption for full disk encryption on desktops, mobile devices and removable storage. If you are looking to start using PGP encryption, this will normally involve downloading a piece of software that automates the process of encryption and decryption. There are a number of different products available to do this, but you should be aware of what to look for.
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