Install the electronic DNI reader

The export of certificates is the process that allows you to obtain a copy of the certificate installed on the computer or in the browser for later use in another computer or process. In the export process we seek or you can mark a box indicating that we want to export the private key. Export must be done from the warehouse is installed on the certificate. In the following points you can see the different ways of accessing the warehouses available on the computer. Applications and Adobe Photoshop allow the validation of signatures contained in pdf documents electronically signed.

However, to make this possible, we need to recognize and Adobe trust in the root certificates of certification authorities have issued certificates with that has been signed the document. For example, to validate correctly a pdf document issued by the BOE is necessary to configure the Adobe environment to recognize the root certificate of FNMT, since it has been this entity which has issued the certificate has signed document of BOE.

Some descriptions of PKC erroneously state that RSA's safety is due to the difficulty in factoring large prime numbers. In fact, large prime numbers, like small prime numbers, only have two factors! The ability for computers to factor large numbers, and therefore attack schemes such as RSA, is rapidly improving and systems today can find the prime factors of numbers with more than digits.

Nevertheless, if a large number is created from two prime factors that are roughly the same size, there is no known factorization algorithm that will solve the problem in a reasonable amount of time; a test to factor a digit number took 1. In , Kleinjung et al.

Certificate store

Even so, they suggested that bit RSA be phased out by See the Wikipedia article on integer factorization. Regardless, one presumed protection of RSA is that users can easily increase the key size to always stay ahead of the computer processing curve. As an aside, the patent for RSA expired in September which does not appear to have affected RSA's popularity one way or the other. A detailed example of RSA is presented below in Section 5.

D-H is used for secret-key key exchange only, and not for authentication or digital signatures. More detail about Diffie-Hellman can be found below in Section 5. Described in FIPS More detail about ECC can be found below in Section 5. These documents are no longer easily available; all links in this section are from archive.

Cramer and V. Shoup of IBM in LUC : A public key cryptosystem designed by P. Smith and based on Lucas sequences. Can be used for encryption and signatures, using integer factoring. McEliece : A public key cryptosystem based on algebraic coding theory. Menezes, P. Vanstone CRC Press, A digression: Who invented PKC?

I tried to be careful in the first paragraph of this section to state that Diffie and Hellman "first described publicly" a PKC scheme. Although I have categorized PKC as a two-key system, that has been merely for convenience; the real criteria for a PKC scheme is that it allows two parties to exchange a secret even though the communication with the shared secret might be overheard. As shown in Section 5. And, indeed, it is the precursor to modern PKC which does employ two keys. Their method, of course, is based upon the relative ease of finding the product of two large prime numbers compared to finding the prime factors of a large number.

Diffie and Hellman and other sources credit Ralph Merkle with first describing a public key distribution system that allows two parties to share a secret, although it was not a two-key system, per se. A Merkle Puzzle works where Alice creates a large number of encrypted keys, sends them all to Bob so that Bob chooses one at random and then lets Alice know which he has selected. An eavesdropper Eve will see all of the keys but can't learn which key Bob has selected because he has encrypted the response with the chosen key. In this case, Eve's effort to break in is the square of the effort of Bob to choose a key.

While this difference may be small it is often sufficient.

Import root certificate in Mozilla Firefox

Merkle apparently took a computer science course at UC Berkeley in and described his method, but had difficulty making people understand it; frustrated, he dropped the course. Merkle's method certainly wasn't published first, but he is often credited to have had the idea first. An interesting question, maybe, but who really knows? Because of the nature of the work, GCHQ kept the original memos classified. In , however, the GCHQ changed their posture when they realized that there was nothing to gain by continued silence. Documents show that a GCHQ mathematician named James Ellis started research into the key distribution problem in and that by , James Ellis, Clifford Cocks, and Malcolm Williamson had worked out all of the fundamental details of PKC, yet couldn't talk about their work.

They were, of course, barred from challenging the RSA patent! Hash functions, also called message digests and one-way encryption , are algorithms that, in essence, use no key Figure 1C. Instead, a fixed-length hash value is computed based upon the plaintext that makes it impossible for either the contents or length of the plaintext to be recovered. Hash algorithms are typically used to provide a digital fingerprint of a file's contents, often used to ensure that the file has not been altered by an intruder or virus.

Hash functions are also commonly employed by many operating systems to encrypt passwords. Hash functions, then, provide a mechanism to ensure the integrity of a file. This is an important distinction. Suppose that you want to crack someone's password, where the hash of the password is stored on the server. Indeed, all you then need is a string that produces the correct hash and you're in!

However, you cannot prove that you have discovered the user's password, only a "duplicate key. Message Digest MD algorithms: A series of byte-oriented algorithms that produce a bit hash value from an arbitrary-length message. MD2 has been relegated to historical status, per RFC MD4 has been relegated to historical status, per RFC MD5 RFC : Also developed by Rivest after potential weaknesses were reported in MD4; this scheme is similar to MD4 but is slower because more manipulation is made to the original data.

MD5 has been implemented in a large number of products although several weaknesses in the algorithm were demonstrated by German cryptographer Hans Dobbertin in "Cryptanalysis of MD5 Compress". In , NIST announced that after reviewing 64 submissions, the winner was Keccak pronounced "catch-ack" , a family of hash algorithms based on sponge functions. The NIST version can support hash output sizes of and bits. Zheng, J. Pieprzyk and J. Seberry, a hash algorithm with many levels of security.

HAVAL can create hash values that are , , , , or bits in length. Whirlpool : Designed by V. Rijmen co-inventor of Rijndael and P. Whirlpool operates on messages less than 2 bits in length and produces a message digest of bits. The design of this hash function is very different than that of MD5 and SHA-1, making it immune to the same attacks as on those hashes. A root hash is used on peer-to-peer file transfer networks, where a file is broken into chunks; each chunk has its own MD4 hash associated with it and the server maintains a file that contains the hash list of all of the chunks.

The root hash is the hash of the hash list file. A digression on hash collisions. Hash functions are sometimes misunderstood and some sources claim that no two files can have the same hash value. This is in theory, if not in fact, incorrect. Consider a hash function that provides a bit hash value.

There are, then, 2 possible hash values. Now, while even this is theoretically correct, it is not true in practice because hash algorithms are designed to work with a limited message size, as mentioned above. Nevertheless, hopefully you get my point. The difficulty is not necessarily in finding two files with the same hash, but in finding a second file that has the same hash value as a given first file.

Consider this example. Since there are more than 7 billion people on earth, we know that there are a lot of people with the same number of hairs on their head. Finding two people with the same number of hairs, then, would be relatively simple. The harder problem is choosing one person say, you, the reader and then finding another person who has the same number of hairs on their head as you have on yours. This is somewhat similar to the Birthday Problem.

Alas, researchers in found that practical collision attacks could be launched on MD5, SHA-1, and other hash algorithms. Readers interested in this problem should read the following:. For historical purposes, take a look at the situation with hash collisions, circa , in RFC In October , the SHA-1 Freestart Collision was announced; see a report by Bruce Schneier and the developers of the attack as well as the paper above by Stevens et al. See also the paper by Stevens et al. Stevens, A. Lenstra, and B. Finally, note that certain extensions of hash functions are used for a variety of information security and digital forensics applications, such as:.

So, why are there so many different types of cryptographic schemes? Why can't we do everything we need with just one? The answer is that each scheme is optimized for some specific cryptographic application s. Hash functions, for example, are well-suited for ensuring data integrity because any change made to the contents of a message will result in the receiver calculating a different hash value than the one placed in the transmission by the sender.

Since it is highly unlikely that two different messages will yield the same hash value, data integrity is ensured to a high degree of confidence. Secret key cryptography, on the other hand, is ideally suited to encrypting messages, thus providing privacy and confidentiality. The sender can generate a session key on a per-message basis to encrypt the message; the receiver, of course, needs the same session key in order to decrypt the message.

Key exchange, of course, is a key application of public key cryptography no pun intended. Asymmetric schemes can also be used for non-repudiation and user authentication; if the receiver can obtain the session key encrypted with the sender's private key, then only this sender could have sent the message. Public key cryptography could, theoretically, also be used to encrypt messages although this is rarely done because secret key cryptography values can generally be computed about times faster than public key cryptography values.

Figure 4 puts all of this together and shows how a hybrid cryptographic scheme combines all of these functions to form a secure transmission comprising a digital signature and digital envelope. In this example, the sender of the message is Alice and the receiver is Bob. A digital envelope comprises an encrypted message and an encrypted session key. Alice uses secret key cryptography to encrypt her message using the session key , which she generates at random with each session.

Alice then encrypts the session key using Bob's public key. The encrypted message and encrypted session key together form the digital envelope. Upon receipt, Bob recovers the session secret key using his private key and then decrypts the encrypted message. The digital signature is formed in two steps.

First, Alice computes the hash value of her message; next, she encrypts the hash value with her private key. Upon receipt of the digital signature, Bob recovers the hash value calculated by Alice by decrypting the digital signature with Alice's public key. Bob can then apply the hash function to Alice's original message, which he has already decrypted see previous paragraph.

If the resultant hash value is not the same as the value supplied by Alice, then Bob knows that the message has been altered; if the hash values are the same, Bob should believe that the message he received is identical to the one that Alice sent. This scheme also provides nonrepudiation since it proves that Alice sent the message; if the hash value recovered by Bob using Alice's public key proves that the message has not been altered, then only Alice could have created the digital signature. Bob also has proof that he is the intended receiver; if he can correctly decrypt the message, then he must have correctly decrypted the session key meaning that his is the correct private key.

This diagram purposely suggests a cryptosystem where the session key is used for just a single session. Even if this session key is somehow broken, only this session will be compromised; the session key for the next session is not based upon the key for this session, just as this session's key was not dependent on the key from the previous session. This is known as Perfect Forward Secrecy ; you might lose one session key due to a compromise but you won't lose all of them.

In a article in the industry literature, a writer made the claim that bit keys did not provide as adequate protection for DES at that time as they did in because computers were times faster in than in Therefore, the writer went on, we needed 56,bit keys in instead of bit keys to provide adequate protection. The conclusion was then drawn that because 56,bit keys are infeasible true , we should accept the fact that we have to live with weak cryptography false!

The major error here is that the writer did not take into account that the number of possible key values double whenever a single bit is added to the key length; thus, a bit key has twice as many values as a bit key because 2 57 is two times 2 In fact, a bit key would have times more values than a bit key. In cryptography, size does matter. The larger the key, the harder it is to crack a block of encrypted data. The reason that large keys offer more protection is almost obvious; computers have made it easier to attack ciphertext by using brute force methods rather than by attacking the mathematics which are generally well-known anyway.

With a brute force attack, the attacker merely generates every possible key and applies it to the ciphertext. Any resulting plaintext that makes sense offers a candidate for a legitimate key. Until the mids or so, brute force attacks were beyond the capabilities of computers that were within the budget of the attacker community. By that time, however, significant compute power was typically available and accessible.

General-purpose computers such as PCs were already being used for brute force attacks. Distributed attacks, harnessing the power of up to tens of thousands of powerful CPUs, are now commonly employed to try to brute-force crypto keys. This information was not merely academic; one of the basic tenets of any security system is to have an idea of what you are protecting and from whom are you protecting it! The table clearly shows that a bit key was essentially worthless against even the most unsophisticated attacker.

PKCS11 module installation - Mozilla | MDN

On the other hand, bit keys were fairly strong unless you might be subject to some pretty serious corporate or government espionage. But note that even bit keys were clearly on the decline in their value and that the times in the table were worst cases. So, how big is big enough? DES, invented in , was still in use at the turn of the century, nearly 25 years later.

If we take that to be a design criteria i. The DES proposal suggested bit keys; by , a bit key would have been required to offer equal protection and an bit key necessary by A or bit SKC key will probably suffice for some time because that length keeps us ahead of the brute force capabilities of the attackers. Note that while a large key is good, a huge key may not always be better; for example, expanding PKC keys beyond the current or bit lengths doesn't add any necessary protection at this time.

Weaknesses in cryptosystems are largely based upon key management rather than weak keys. Blaze, W. Diffie, R. Rivest, B. Schneier, T. Shimomura, E. Thompson, and M. Wiener The most effective large-number factoring methods today use a mathematical Number Field Sieve to find a certain number of relationships and then uses a matrix operation to solve a linear equation to produce the two prime factors. The sieve step actually involves a large number of operations that can be performed in parallel; solving the linear equation, however, requires a supercomputer.

In early , Shamir of RSA fame described a new machine that could increase factorization speed by orders of magnitude. There still appear to be many engineering details that have to be worked out before such a machine could be built. Furthermore, the hardware improves the sieve step only; the matrix operation is not optimized at all by this design and the complexity of this step grows rapidly with key length, both in terms of processing time and memory requirements.

Nevertheless, this plan conceptually puts bit keys within reach of being factored. It is also interesting to note that while cryptography is good and strong cryptography is better, long keys may disrupt the nature of the randomness of data files. Shamir and van Someren "Playing hide and seek with stored keys" have noted that a new generation of viruses can be written that will find files encrypted with long keys, making them easier to find by intruders and, therefore, more prone to attack.

Finally, U. Until the mids, export outside of North America of cryptographic products using keys greater than 40 bits in length was prohibited, which made those products essentially worthless in the marketplace, particularly for electronic commerce; today, crypto products are widely available on the Internet without restriction. The U. Department of Commerce Bureau of Industry and Security maintains an Encryption FAQ web page with more information about the current state of encryption registration.

Without meaning to editorialize too much in this tutorial, a bit of historical context might be helpful. In the mids, the U. Department of Commerce still classified cryptography as a munition and limited the export of any products that contained crypto. For that reason, browsers in the era, such as Internet Explorer and Netscape, had a domestic version with bit encryption downloadable only in the U.

Many cryptographers felt that the export limitations should be lifted because they only applied to U. Those restrictions were lifted by or , but there is still a prevailing attitude, apparently, that U. On a related topic, public key crypto schemes can be used for several purposes, including key exchange, digital signatures, authentication, and more. The length of the secret keys exchanged via that system have to have at least the same level of attack resistance. Secure use of cryptography requires trust. While secret key cryptography can ensure message confidentiality and hash codes can ensure integrity, none of this works without trust.

PKC solved the secret distribution problem, but how does Alice really know that Bob is who he says he is? Just because Bob has a public and private key, and purports to be "Bob," how does Alice know that a malicious person Mallory is not pretending to be Bob? There are a number of trust models employed by various cryptographic schemes. This section will explore three of them:. Each of these trust models differs in complexity, general applicability, scope, and scalability. Pretty Good Privacy described more below in Section 5. A PGP user maintains a local keyring of all their known and trusted public keys.

The user makes their own determination about the trustworthiness of a key using what is called a "web of trust. If Alice needs Bob's public key, Alice can ask Bob for it in another e-mail or, in many cases, download the public key from an advertised server; this server might a well-known PGP key repository or a site that Bob maintains himself. In fact, Bob's public key might be stored or listed in many places. Alice is prepared to believe that Bob's public key, as stored at these locations, is valid. Suppose Carol claims to hold Bob's public key and offers to give the key to Alice.

How does Alice know that Carol's version of Bob's key is valid or if Carol is actually giving Alice a key that will allow Mallory access to messages? The answer is, "It depends. And trust is not necessarily transitive; if Dave has a copy of Bob's key and Carol trusts Dave, it does not necessarily follow that Alice trusts Dave even if she does trust Carol.

The point here is that who Alice trusts and how she makes that determination is strictly up to Alice. PGP makes no statement and has no protocol about how one user determines whether they trust another user or not. In any case, encryption and signatures based on public keys can only be used when the appropriate public key is on the user's keyring.

Kerberos is a commonly used authentication scheme on the Internet. Developed by MIT's Project Athena, Kerberos is named for the three-headed dog who, according to Greek mythology, guards the entrance of Hades rather than the exit, for some reason! In this model, security and authentication will be based on secret key technology where every host on the network has its own secret key. It would clearly be unmanageable if every host had to know the keys of all other hosts so a secure, trusted host somewhere on the network, known as a Key Distribution Center KDC , knows the keys for all of the hosts or at least some of the hosts within a portion of the network, called a realm.

In this way, when a new node is brought online, only the KDC and the new node need to be configured with the node's key; keys can be distributed physically or by some other secure means. The steps in establishing an authenticated session between an application client and the application server are:. While the details of their operation, functional capabilities, and message formats are different, the conceptual overview above pretty much holds for both. One primary difference is that Kerberos V4 uses only DES to generate keys and encrypt messages, while V5 allows other schemes to be employed although DES is still the most widely algorithm used.

Certificates and Certificate Authorities CA are necessary for widespread use of cryptography for e-commerce applications. While a combination of secret and public key cryptography can solve the business issues discussed above, crypto cannot alone address the trust issues that must exist between a customer and vendor in the very fluid, very dynamic e-commerce relationship. How, for example, does one site obtain another party's public key? How does a recipient determine if a public key really belongs to the sender?

How does the recipient know that the sender is using their public key for a legitimate purpose for which they are authorized? When does a public key expire? How can a key be revoked in case of compromise or loss? The basic concept of a certificate is one that is familiar to all of us. A driver's license, credit card, or SCUBA certification, for example, identify us to others, indicate something that we are authorized to do, have an expiration date, and identify the authority that granted the certificate.

As complicated as this may sound, it really isn't. Consider driver's licenses. I have one issued by the State of Florida. The license establishes my identity, indicates the type of vehicles that I can operate and the fact that I must wear corrective lenses while doing so, identifies the issuing authority, and notes that I am an organ donor.

When I drive in other states, the other jurisdictions throughout the U. When I leave the U. When I am in Aruba, Australia, Canada, Israel, and many other countries, they will accept not the Florida license, per se, but any license issued in the U. This analogy represents the certificate trust chain, where even certificates carry certificates. For purposes of electronic transactions, certificates are digital documents.

The specific functions of the certificate include: Establish identity: Associate, or bind , a public key to an individual, organization, corporate position, or other entity. Assign authority: Establish what actions the holder may or may not take based upon this certificate.

Secure confidential information e. A sample abbreviated certificate is shown in Figure 6. While this is a certificate issued by VeriSign, many root-level certificates can be found shipped with browsers.


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When the browser makes a connection to a secure Web site, the Web server sends its public key certificate to the browser. The browser then checks the certificate's signature against the public key that it has stored; if there is a match, the certificate is taken as valid and the Web site verified by this certificate is considered to be "trusted. Most certificates today comply with X.

Certificate authorities are the repositories for public keys and can be any agency that issues certificates. When a sender needs an intended receiver's public key, the sender must get that key from the receiver's CA. That scheme is straight-forward if the sender and receiver have certificates issued by the same CA.

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If not, how does the sender know to trust the foreign CA? One industry wag has noted, about trust: "You are either born with it or have it granted upon you. CAs, in turn, form trust relationships with other CAs. Thus, if a user queries a foreign CA for information, the user may ask to see a list of CAs that establish a "chain of trust" back to the user. One major feature to look for in a CA is their identification policies and procedures.

When a user generates a key pair and forwards the public key to a CA, the CA has to check the sender's identification and takes any steps necessary to assure itself that the request is really coming from the advertised sender. Different CAs have different identification policies and will, therefore, be trusted differently by other CAs. Verification of identity is just one of many issues that are part of a CA's Certification Practice Statement CPS and policies; other issues include how the CA protects the public keys in its care, how lost or compromised keys are revoked, and how the CA protects its own private keys.

As a final note, CAs are not immune to attack and certificates themselves are able to be counterfeited. Problems have continued over the years; good write-ups on this can be found at " Another Certification Authority Breached the 12th! The paragraphs above describe three very different trust models. It is hard to say that any one is better than the others; it depends upon your application. One of the biggest and fastest growing applications of cryptography today, though, is electronic commerce e-commerce , a term that itself begs for a formal definition.

PGP's web of trust is easy to maintain and very much based on the reality of users as people. The model, however, is limited; just how many public keys can a single user reliably store and maintain? And what if you are using the "wrong" computer when you want to send a message and can't access your keyring? How easy it is to revoke a key if it is compromised? PGP may also not scale well to an e-commerce scenario of secure communication between total strangers on short-notice. Kerberos overcomes many of the problems of PGP's web of trust, in that it is scalable and its scope can be very large.

In the early days of the Internet, every host had to maintain a list of every other host; the Domain Name System DNS introduced the idea of a distributed database for this purpose and the DNS is one of the key reasons that the Internet has grown as it has. While certificates and the benefits of a PKI are most often associated with electronic commerce, the applications for PKI are much broader and include secure electronic mail, payments and electronic checks, Electronic Data Interchange EDI , secure transfer of Domain Name System DNS and routing information, electronic forms, and digitally signed documents.

A single "global PKI" is still many years away, that is the ultimate goal of today's work as international electronic commerce changes the way in which we do business in a similar way in which the Internet has changed the way in which we communicate. The paragraphs above have provided an overview of the different types of cryptographic algorithms, as well as some examples of some available protocols and schemes.

The paragraphs below will show several real cryptographic applications that many of us employ knowingly or not everyday for password protection and private communication. Some of the schemes described below never were widely deployed but are still historically interesting, thus remain included here. But passwords are not typically kept on a host or server in plaintext, but are generally encrypted using some sort of hash scheme.

Note that each password is stored as a byte string. The first two characters are actually a salt , randomness added to each password so that if two users have the same password, they will still be encrypted differently; the salt, in fact, provides a means so that a single password might have different encryptions. The remaining 11 bytes are the password hash, calculated using DES. This fact, coupled with the weak encryption of the passwords, resulted in the development of the shadow password system where passwords are kept in a separate, non-world-readable file used in conjunction with the normal password file.

In the NT case, all passwords are hashed using the MD4 algorithm, resulting in a bit byte hash value they are then obscured using an undocumented mathematical transformation that was a secret until distributed on the Internet. The password password , for example, might be stored as the hash value in hexadecimal b22d73c34bd4aa79c8b09f Passwords are not saved in plaintext on computer systems precisely so they cannot be easily compromised.

For similar reasons, we don't want passwords sent in plaintext across a network. But for remote logon applications, how does a client system identify itself or a user to the server? One mechanism, of course, is to send the password as a hash value and that, indeed, may be done. A weakness of that approach, however, is that an intruder can grab the password off of the network and use an off-line attack such as a dictionary attack where an attacker takes every known word and encrypts it with the network's encryption algorithm, hoping eventually to find a match with a purloined password hash.

In some situations, an attacker only has to copy the hashed password value and use it later on to gain unauthorized entry without ever learning the actual password. An even stronger authentication method uses the password to modify a shared secret between the client and server, but never allows the password in any form to go across the network. As suggested above, Windows NT passwords are stored in a security file on a server as a byte hash value.

When a user logs on to a server from a remote workstation, the user is identified by the username, sent across the network in plaintext no worries here; it's not a secret anyway! The server then generates a bit random number and sends it to the client also in plaintext. This number is the challenge. Recall that DES employs a bit key, acts on a bit block of data, and produces a bit output. In this case, the bit data block is the random number.

The client actually uses three different DES keys to encrypt the random number, producing three different bit outputs. The first key is the first seven bytes 56 bits of the password's hash value, the second key is the next seven bytes in the password's hash, and the third key is the remaining two bytes of the password's hash concatenated with five zero-filled bytes.

So, for the example above, the three DES keys would be b22d73c34 , bd4aa79c8b0 , and 9f Each key is applied to the random number resulting in three bit outputs, which comprise the response. Thus, the server's 8-byte challenge yields a byte response from the client and this is all that would be seen on the network. The server, for its part, does the same calculation to ensure that the values match. There is, however, a significant weakness to this system. Specifically, the response is generated in such a way as to effectively reduce byte hash to three smaller hashes, of length seven, seven, and two, respectively.

Thus, a password cracker has to break at most a 7-byte hash. One Windows NT vulnerability test program that I used in the past reported passwords that were "too short," defined as "less than 8 characters. This was, in fact, not the case at all; all the software really had to do was to look at the last eight bytes of the Windows NT LanMan hash to see that the password was seven or fewer characters.

Consider the following example, showing the LanMan hash of two different short passwords take a close look at the last 8 bytes :. MS-CHAP assumes that it is working with hashed values of the password as the key to encrypting the challenge. Diffie and Hellman introduced the concept of public key cryptography.

The mathematical "trick" of Diffie-Hellman key exchange is that it is relatively easy to compute exponents compared to computing discrete logarithms.

Diffie-Hellman works like this. Alice and Bob start by agreeing on a large prime number, N. There is actually another constraint on G, namely that it must be primitive with respect to N. As an example, 2 is not primitive to 7 because the set of powers of 2 from 1 to 6, mod 7 i. The definition of primitive introduced a new term to some readers, namely mod. The phrase x mod y and read as written! Read more about the modulo function in the appendix. Anyway, either Alice or Bob selects N and G; they then tell the other party what the values are.

Alice and Bob then work independently:.

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The particular rules aren't as important as following them strictly is, but if you can sacrifice your peculiar preferences to be consistent with the rest of the world , your contributors will appreciate it a lot. I also practice slow-food Take your time, enjoy the journey to mastering this craft, and when you've built something you can proudly set free, let the masses read it and judge it. Write unit tests. Tons of them. This might sound extreme, but hey, your code is now playing directly with somebody else's money.

If you forget, or just get lazy and don't write a test for that super obvious line of code, you might be leaving an open door for an exploit later in the game that will make your project crash, and all this magic internet money will disappear in no time. It has happened. I feel immediately more secure when I do test-driven development. At least give an honest try to writing the tests first, and get into a cycle of red-green-refactor. There are other techniques that can achieve the same result, but I suggest starting there and then deviating if you find good reasons to do so. Never worked this way?

It's a quick read that will help you avoid the temptation of just jumping into code without thinking it through. Then, even if you design for testability, you'll find many scenarios that are hard to test. Gerard Meszaros provides all the answers in xUnit Test Patterns. This book is huge, so I recommend choosing a designated test expert on your team. Finally, make sure to run your unit tests on every single pull request, and make sure they're all green before merging the changes.

In addition, you can set up a test coverage report to ensure that test coverage never goes down. Now that you have your first layer of tests covered with tons of unit tests, what comes next is You need to test the integration between all of your components, then go one level higher to test your application from the point of view of a real user, and then go even higher to test the interactions with other systems end-to-end. To me, this is the biggest challenge, and designing a good process that keeps many bugs out of your system can be as difficult as designing the system itself. Iterate, automate as much as possible, share the load of manual testing We'll talk later about community, but I think this is the reason for publishing your code as early as possible: you can get help from early adopters and enthusiasts to validate your system, not only for correctness but also to verify that you're focusing on the right user stories and that you're tackling a real problem with a user-friendly solution.

A lot has been written about iterative development processes that deliver functionalities in progressive sprints and milestones. I found Mike Cohn's Succeeding with Agile: Software Development Using Scrum a good place to start, but keep in mind that any methodology will have to be adjusted to your team, your users, and your context.


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There are a lot fewer resources focused on the quality and testing part; that's why I was so happy when I read Agile Testing by Lisa Crispin and Janet Gregory, which is full of good ideas and advice. But let me stress again: nothing you read will perfectly fit your project, so take your time to design the testing process with as much love and care as you use when designing the system's architecture.

While there's still some debate about the perfect moment for auditing a project i. I see room for auditing before the code has been published, but in this case, the audit would be more related to checking that the development process will lead to a high-quality, properly tested release candidate and validating the bases of your project than to performing a deep and thorough inspection of the codebase.

Once you start writing and testing clean code in incremental iterations, it becomes easier to think about your complex system. Many smaller independent parts will start to pop up, which can be extracted, generalized, and packaged for reuse, reducing anxiety for developers and auditors. This is my least favorite part, by far. And yet, it's usually either empty or bloated, outdated, and ugly.

Ideally, as it's the first thing developers and potential contributors will read, it should work as a clear, straightforward index of your project. It's best not to get creative here. Just follow this simple specification that works for all cases, proposed by Richard Littauer in Standard Readme.


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Do not forget to include a specific section in the main README that states how people should disclose any security vulnerabilities found in your project. Next come the docstrings, the documentation inside your code files. We hit an apparent conflict here, since in theory, if your code is clean, it will not require documentation. However, note that we are no longer designing standalone systems that work as a black box.

We are building protocols for decentralized applications, and your code will be called by all sorts of external agents. So by all means, document every function that's part of the contract's public API, following the NatSpec format. Which brings me to the next point. I highly recommend that you document the specification of your protocol—that's how others will know what to call and what to expect. But more related to the topic at hand, in an audit, we check that the implemented code works as intended by the specification. That's why this document is a must : without it, auditors will just guess at your intentions, which might result in some issues getting missed because they're completely consistent within the system but take it to a state that you want to avoid.

Finally, there's the user documentation. For high-quality systems, writing the user documentation should be mostly painless. The moment things get cumbersome while documenting, consider re-evaluating your user stories, and don't be afraid to go back to iterate on them.