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8. 10. 2024

Security Cryptography

Local authentication in *NIX (crypt interface)

The Crypt interface is one of the most popular interfaces designed to protect stored passwords.

Evolution of Crypt interface

The original version of Crypt from Unix V7 (Unix Version 7) dates back to 1979. At that time, it only supported one-way password storage using a modified version of the DES algorithm. In older versions, password storage was used in open form. The introduction of the Crypt interface was a significant improvement and gradually expanded to include other algorithms. Subsequently, this interface was also used for authentication by different systems, which is not primarily intended for. Around 2010, it was discovered that the currently used methods of storing passwords were not sufficient to meet the requirements and a search for replacements began. A significant change was brought about by Password Hashing Competition, initiated in 2013 and finished in 2015. He aimed to find a specific class of slow hash functions. That is, groups of functions for which it is difficult to create a rainbow table (a form of computing time-memory trade-off).

Another extension was provided by glibc 2.7, when an additional parameter was added, containing a user-defined number of rund hashes of the function. Currently, the crypt interface uses a general hash string record format of the password '$ID$parameter_2$parameter_3$password_hash'. The number of parameters in this string may vary according to the ID of the algorithm chosen (see the overview for more). However, previous versions did not offer this option, so older systems can still encounter the structure '$ID$parameter_2$password_hash'. In this case, salt is usually inserted as parameter no.2.

Algorithm	Schema ID	Schema	Rounds	Salt	Description
DES	_	BSDI	1	24b, parameter n.3	Weak and obsolete
DES		DES	25	12b, parameter n.3	Weak and obsolete
MD5	$1$	MD5		parameter n.2	Weak and obsolete
Blowfish	$2$	bcrypt	parameter n.2	part of hash	Password <72 chars, obsolete
Blowfish	$2a$	bcrypt	parameter n.2	part of hash	Password <72 chars, CVE-2011-2483, obsolete
Blowfish	$2b$	bcrypt	parameter n.2	part of hash	Password <72 chars, obsolete
Blowfish	$2x$	bcrypt	parameter n.2	part of hash	Password <72 chars
Blowfish	$2y$	bcrypt	parameter n.2	part of hash	Password <72 chars
MD4	$3$	NTHASH			Weak, MD4(UNICODE(password))
SHA1	$4$	SHA1	parameter n.2	parameter n.3	Weak
SHA2	$5$	SHA2-256	parameter n.2	parameter n.3
SHA2	$6$	SHA2-512	parameter n.2	parameter n.3
scrypt	$7$	scrypt	parameter n.2
MD5	$md5,rounds=x$	Solaris MD5	parameter n.2	parameter n.3	Weak
SHA1	$sha1$	PBKDF1 with SHA2-256	parameter n.2	parameter n.3	Weak
SHA2	$sha256$	PBKDF2 with SHA2-256	parameter n.2	parameter n.3
SHA2	$sha512$	PBKDF2 with SHA2-512	parameter n.2	parameter n.3
ARGON2D	$argon2d$	Argon2d	parameter n.2	parameter n.3
ARGON2I	$argon2i$	Argon2i	parameter n.2	parameter n.3
yescrypt	$gy$	ghost-yescrypt	parameter n.2	parameter n.3	Weakened - Streebog S-Box
yescrypt	$y$	yescrypt	parameter n.2	parameter n.3

Local Authentication

Currently, Crypt interfaces are used as "local authentication" by various web, mail, and database systems. These interfaces rely on their own password storage, or system or hierarchical databases (LDAP). But these functions are intended for the storage and authentication of password hashes, where they are backdoor functions, otherwise also one-way functions. Their extension for network authentication was unfortunate, although it is a much safer procedure than for passwords in open text. The authentication mechanism must provide significantly more requests than just one-way storage.
From today's perspective, the use of old technologies is inappropriate. The current use of pure hash functions is insufficient, as is the insufficient use of HMAC or PBKDF derivation. From a security point of view, it is necessary to focus only on scrypt, yescrypt, and Argon. On older implementations, the older bcrypt can be "at the mercy" of the older bcrypt. Despite its archaic design, it is still effective, although from the cryptographic point of view it would be advisable to replace it with more modern systems.
The aforementioned Password Hashing Competition (PHC) aimed at finding slow hash functions (Slow Hash Functions) has brought interesting progress. Some of these functions, designed to secure key material, were able to resist the design, although at first glance their architecture is slightly archaic. An example is bcrypt, based on the BlowFish algorithm (more precisely EksBlowfish - Expensive Key Schedule Blowfish), although the Blowfish itself is considered obsolete from the cryptographic point of view. A new feature in this area was the scrypt algorithm, built over PBKDF2 and HMAC-SHA256, and the Salsa20/8 algorithm (predecessor of ChaCha20). The scrypt algorithm creates a higher memory intensity, which serves as an additional barrier for the attacker. Another similar algorithm is yescrypt, which again uses PBKDF2 and HMAC-SHA256. Compared to the scrypt algorithm, it has a significantly higher resistance. The winner, the Argon algorithm is built over the then new Blake2 hashing function (inspired by ChaCha20 and Salsa algorithms).
In this competition, features available at the time such as bcrypt, scrypt, yescrypt, Catena, Lyra2, Makwa, Argon2 and others were compared. In this respect, the Argon2 feature excels, which has several variants:
Argon2i – resistant to side channel attack.
Argon2d – resistant to bruteforce cracking attacks, usually with the help of graphics cards.
Argon2id – a compromise combination of these features.

Reference:

Password Hashing Competition.
Zdroj: https://www.password-hashing.net/
Crypt man pages.
Zdroj: https://man7.org/linux/man-pages/man3/crypt.3.html

Autor článku:

Jan Dušátko

Jan Dušátko has been working with computers and computer security for almost a quarter of a century. In the field of cryptography, he has cooperated with leading experts such as Vlastimil Klíma or Tomáš Rosa. Currently he works as a security consultant, his main focus is on topics related to cryptography, security, e-mail communication and Linux systems.

1. Introductory Provisions

1.1. These General Terms and Conditions are, unless otherwise agreed in writing in the contract, an integral part of all contracts relating to training organised or provided by the trainer, Jan Dušátko, IČ 434 797 66, DIČ 7208253041, with location Pod Harfou 938/58, Praha 9 (next as a „lector“).
1.2. The contracting parties in the general terms and conditions are meant to be the trainer and the ordering party, where the ordering party may also be the mediator of the contractual relationship.
1.3. Issues that are not regulated by these terms and conditions are dealt with according to the Czech Civil Code, i.e. Act No.89/2012 Coll.
1.4. All potential disputes will be resolved according to the law of the Czech Republic.

2. Creation of a contract by signing up for a course

2.1. Application means unilateral action of the client addressed to the trainer through a data box with identification euxesuf, e-mailu with address register@cryptosession.cz or register@cryptosession.info, internet pages cryptosession.cz, cryptosession.info or contact phone +420 602 427 840.
2.2. By submitting the application, the Client agrees with these General Terms and Conditions and declares that he has become acquainted with them.
2.3. The application is deemed to have been received at the time of confirmation (within 2 working days by default) by the trainer or intermediary. This confirmation is sent to the data box or to the contact e-mail.
2.4. The standard time for registration is no later than 14 working days before the educational event, unless otherwise stated. In the case of a natural non-business person, the order must be at least 28 working days before the educational event.
2.5. More than one participant can be registered for one application.
2.6. If there are more than 10 participants from one Client, it is possible to arrange for training at the place of residence of the intermediary or the Client.
2.7. Applications are received and processed in the order in which they have been received by the Provider. The Provider immediately informs the Client of all facts. These are the filling of capacity, too low number of participants, or any other serious reason, such as a lecturer's illness or force majeure. In this case, the Client will be offered a new term or participation in another educational event. In the event that the ordering party does not agree to move or participate in another educational event offered, the provider will refund the participation fee. The lack of participants is notified to the ordering party at least 14 days before the start of the planned term.
2.8. The contract between the provider and the ordering party arises by sending a confirmation from the provider to the ordering party.
2.9. The contract may be changed or cancelled only if the legal prerequisites are met and only in writing.

3. Termination of the contract by cancellation of the application

3.1. The application may be cancelled by the ordering party via e-mail or via a data mailbox.
3.2. The customer has the right to cancel his or her application for the course 14 days before the course takes place without any fees. If the period is shorter, the subsequent change takes place. In the interval of 7-13 days, an administrative fee of 10% is charged, cancellation of participation in a shorter interval than 7 days then a fee of 25%. In case of cancellation of the application or order by the customer, the possibility of the customer's participation in an alternative period without any additional fee is offered. The right to cancel the application expires with the implementation of the ordered training.
3.3. In case of cancellation of the application by the trainer, the ordering party is entitled to a full refund for the unrealized action.
3.4. The ordering party has the right to request an alternative date or an alternative training. In such case, the ordering party will be informed about all open courses. The alternative date cannot be enforced or enforced, it depends on the current availability of the course. If the alternative training is for a lower price, the ordering party will pay the difference. If the alternative training is for a lower price, the trainer will return the difference in the training prices to the ordering party.

4. Price and payment terms

4.1. By sending the application, the ordering party accepts the contract price (hereinafter referred to as the participation fee) indicated for the course.
4.2. In case of multiple participants registered with one application, a discount is possible.
4.3. The participation fee must be paid into the bank account of the company held with the company Komerční banka č. 78-7768770207/0100, IBAN:CZ5301000000787768770207, BIC:KOMBCZPPXXX. When making the payment, a variable symbol must be provided, which is indicated on the invoice sent to the client by the trainer.
4.4. The participation fee includes the provider's costs, including the training materials. The provider is a VAT payer.
4.5. The client is obliged to pay the participation fee within 14 working days of receipt of the invoice, unless otherwise stated by a separate contract.
4.6. If the person enrolled does not attend the training and no other agreement has been made, his or her absence is considered a cancellation application at an interval of less than 7 days, i.e. the trainer is entitled to a reward of 25% of the course price. The overpayment is returned within 14 days to the sender's payment account from which the funds were sent. Payment to another account number is not possible.
4.7. An invoice will be issued by the trainer no later than 5 working days from the beginning of the training, which will be sent by e-mail or data box as agreed.

5. Training conditions

5.1. The trainer is obliged to inform the client 14 days in advance of the location and time of the training, including the start and end dates of the daily programme.
5.2. If the client is not a student of the course, he is obliged to ensure the distribution of this information to the end participants. The trainer is not responsible for failure to comply with these terms and conditions.
5.2. By default, the training takes place from 9 a.m. to 5 p.m. at a predetermined location.
5.3. The trainer can be available from 8 a.m. to 9 a.m. and then from 17 a.m. to 6 p.m. for questions from the participants, according to the current terms and conditions.
5.4. At the end of the training, the certificate of absorption is handed over to the end users.
5.5. At the end of the training, the end users evaluate the trainer's approach and are asked to comment on the evaluation of his presentation, the manner of presentation and the significance of the information provided.

6. Complaints

6.1. If the participant is grossly dissatisfied with the course, the trainer is informed of this information.
6.2. The reasons for dissatisfaction are recorded in the minutes in two copies on the same day. One is handed over to the client and one is held by the trainer.
6.3. A statement on the complaint will be submitted by e-mail within two weeks. A solution will then be agreed within one week.
6.4. The customer's dissatisfaction may be a reason for discontinuing further cooperation, or financial compensation up to the price of the training, after deduction of costs.

7. Copyright of the provided materials

7.1. The training materials provided by the trainer in the course of the training meet the characteristics of a copyrighted work in accordance with Czech Act No 121/2000 Coll.
7.2. None of the training materials or any part thereof may be further processed, reproduced, distributed or used for further presentations or training in any way without the prior written consent of the trainer.

8. Liability

8.1. The trainer does not assume responsibility for any shortcomings in the services of any third party that he uses in the training.
8.2. The trainer does not assume responsibility for injuries, damages and losses incurred by the participants in the training events or caused by the participants. Such costs, caused by the above circumstances, shall be borne exclusively by the participant in the training event.

9. Validity of the Terms

9.1 These General Terms and Conditions shall be valid and effective from 1 October 2024.

Consent to the collection and processing of personal data

According to Regulation (EU) No 2016/679 of the European Parliament and of the Council on the protection of individuals with regard to the processing of personal data and on the free movement of such data and repealing Directive 95/46/EC (General Data Protection Regulation, hereinafter referred to as "the Regulation"), the processor xxx (hereinafter referred to as "the Controller") processes personal data. Individual personal data that are part of the processing during specific activities at this web presentation and in the course of trade are also broken down.
Although the collection of data is ubiquitous, the operation of this website is based on the right to privacy of each user. For this reason, the collection of information about users takes place to the extent absolutely necessary and only if the user decides to contact the operator. We consider any further collection and processing of data unethical.

Information about the records of access to the web presentation

This website does not collect any cookies. The site does not use any analytical scripts of third parties (social networks, cloud providers). For these reasons, an option is also offered for displaying the map in the form of a link, where the primary source is OpenStreet and alternatives then the frequently used Maps of Seznam, a.s., or Google Maps of Google LLC Inc. The use of any of these sources is entirely at the discretion of the users of this site. The administrator is not responsible for the collection of data carried out by these companies, does not provide them with data about users and does not cooperate on the collection of data.
Logging of access takes place only at the system level, the reason being the identification of any technical or security problems. Other reasons are overview access statistics. No specific data is collected or monitored in this area and all access records are deleted after three months.

Information about contacting the operator of the site

The form for contacting the operator of the site (administrator) contains the following personal data: name, surname, e-mail. These data are intended only for this communication, corresponding to the address of the user and are kept for the time necessary to fulfil the purpose, up to a maximum of one year, unless the user determines otherwise.

Information about the order form

In case of an interest in the order form, the form contains more data, i.e. name, surname, e-mail and contact details for the organisation. These data are intended only for this communication, corresponding to the address of the user and are kept for one year, unless the user determines otherwise. In the event that a business relationship is concluded on the basis of this order, only the information required by Czech law on the basis of business relations (company name and address, bank account number, type of course and its price) will continue to be kept by the administrator.

Information about the course completion document

Within the course, a course completion document is issued by the processor. This document contains the following data: student's name and surname, the name and date of the course completion and the employer's name. The information is subsequently used for the creation of a linear hash tree (non-modifiable record). This database contains only information about the provided names and company names, which may or may not correspond to reality and is maintained by the processor for possible re-issuance or verification of the document's issuance.

Rights of the personal data subject

The customer or visitor of this website has the possibility to request information about the processing of personal data, the right to request access to personal data, or the right to request the correction or deletion of any data held about him. In the case of deletion, this requirement cannot be fulfilled only if it is not data strictly necessary in the course of business. The customer or visitor of this website also has the right to obtain explanations regarding the processing of his personal data if he finds out or believes that the processing is carried out in violation of the protection of his private and personal life or in violation of applicable legislation, and the right to request removal of the resulting situation and to ensure the correction.
Furthermore, the customer/visitor of this website may request restriction of processing or object to the processing of personal data and has the right to withdraw his/her consent to the processing of personal data at any time in writing, without prejudice to the lawfulness of their processing prior to such withdrawal. For this purpose, the contact e-mail address support@cryptosession.cz is used.
The customer/visitor has the right to file a complaint against the processing of personal data with the supervisory authority, which is the Office for Personal Data Protection.

Blog

Local authentication in *NIX (crypt interface)

Evolution of Crypt interface

Local Authentication

Reference:

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