Go beyond the iconic crack to learn how this State House bell was transformed into an extraordinary symbol. Abolitionists, women's suffrage advocates and Civil Rights leaders took inspiration from the inscription on this bell. Plan your visit to the Liberty Bell Center to allow time to view the exhibits, see the film, and gaze upon the famous cracked bell. No tickets are required and hours vary seasonally.
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From Signal to Symbol The State House bell, now known as the Liberty Bell, rang in the tower of the Pennsylvania State House. Today, we call that building Independence Hall. Speaker of the Pennsylvania Assembly Isaac Norris first ordered a bell for the bell tower in 1751 from the Whitechapel Foundry in London. That bell cracked on the first test ring. Local metalworkers John Pass and John Stow melted down that bell and cast a new one right here in Philadelphia. It's this bell that would ring to call lawmakers to their meetings and the townspeople together to hear the reading of the news. Benjamin Franklin wrote to Catherine Ray in 1755, "Adieu, the Bell rings, and I must go among the Grave ones and talk Politicks." It's not until the 1830s that the old State House bell would begin to take on significance as a symbol of liberty.
The Crack No one recorded when or why the Liberty Bell first cracked, but the most likely explanation is that a narrow split developed in the early 1840s after nearly 90 years of hard use. In 1846, when the city decided to repair the bell prior to George Washington's birthday holiday (February 23), metal workers widened the thin crack to prevent its farther spread and restore the tone of the bell using a technique called "stop drilling". The wide "crack" in the Liberty Bell is actually the repair job! Look carefully and you'll see over 40 drill bit marks in that wide "crack". But, the repair was not successful. The Public Ledger newspaper reported that the repair failed when another fissure developed. This second crack, running from the abbreviation for "Philadelphia" up through the word "Liberty", silenced the bell forever. No one living today has heard the bell ring freely with its clapper, but computer modeling provides some clues into the sound of the Liberty Bell.
The Meaning The State House bell became a herald of liberty in the 19th century. "Proclaim Liberty Throughout All the Land Unto All the Inhabitants thereof," the bell's inscription, provided a rallying cry for abolitionists wishing to end slavery. The Anti-Slavery Record, an abolitionist publication, first referred to the bell as the Liberty Bell in 1835, but that name was not widely adopted until years later. Millions of Americans became familiar with the bell in popular culture through George Lippard's 1847 fictional story "Ring, Grandfather, Ring", when the bell came to symbolize pride in a new nation. Beginning in the late 1800s, the Liberty Bell traveled across the country for display at expositions and fairs, stopping in towns small and large along the way. For a nation recovering from wounds of the Civil War, the bell served to remind Americans of a time when they fought together for independence. Movements from Women's Suffrage to Civil Rights embraced the Liberty Bell for both protest and celebration. Pennsylvania suffragists commissioned a replica of the Liberty Bell. Their "Justice Bell" traveled across Pennsylvania in 1915 to encourage support for women's voting rights legislation. It then sat chained in silence until the passage of the 19th Amendment in 1920. Now a worldwide symbol, the bell's message of liberty remains just as relevant and powerful today: "Proclaim Liberty Throughout All the Land Unto All the Inhabitants thereof"
EFFECTIVE DATE: Upon passage, with the provision allowing suit against certain insurers for up to one year after a claim denial is applicable to policies issued, renewed, or in effect on or after the bill's effective date; and the tax deduction provisions applicable to taxable years beginning on or after January 1, 2017
It is essential to store passwords in a way that prevents them from being obtained by an attacker even if the application or database is compromised. The majority of modern languages and frameworks provide built-in functionality to help store passwords safely.
After an attacker has acquired stored password hashes, they are always able to brute force hashes offline. As a defender, it is only possible to slow down offline attacks by selecting hash algorithms that are as resource intensive as possible.
Hashing is a one-way function (i.e., it is impossible to "decrypt" a hash and obtain the original plaintext value). Hashing is appropriate for password validation. Even if an attacker obtains the hashed password, they cannot enter it into an application's password field and log in as the victim.
In the context of password storage, encryption should only be used in edge cases where it is necessary to obtain the original plaintext password. This might be necessary if the application needs to use the password to authenticate with another system that does not support a modern way to programmatically grant access, such as OpenID Connect (OIDC). Where possible, an alternative architecture should be used to avoid the need to store passwords in an encrypted form.
While the number of permutations can be enormous, with high speed hardware (such as GPUs) and cloud services with many servers for rent, the cost to an attacker is relatively small to do successful password cracking especially when best practices for hashing are not followed.
Strong passwords stored with modern hashing algorithms and using hashing best practices should be effectively impossible for an attacker to crack. It is your responsibility as an application owner to select a modern hashing algorithm.
A salt is a unique, randomly generated string that is added to each password as part of the hashing process. As the salt is unique for every user, an attacker has to crack hashes one at a time using the respective salt rather than calculating a hash once and comparing it against every stored hash. This makes cracking large numbers of hashes significantly harder, as the time required grows in direct proportion to the number of hashes.
Salting also protects against an attacker pre-computing hashes using rainbow tables or database-based lookups. Finally, salting means that it is impossible to determine whether two users have the same password without cracking the hashes, as the different salts will result in different hashes even if the passwords are the same.
A pepper can be used in addition to salting to provide an additional layer of protection. The purpose of the pepper is to prevent an attacker from being able to crack any of the hashes if they only have access to the database, for example, if they have exploited a SQL injection vulnerability or obtained a backup of the database.
One of several peppering strategies is to hash the passwords as usual (using a password hashing algorithm) and then HMAC or encrypt the hashes with a symmetrical encryption key before storing the password hash in the database, with the key acting as the pepper. Peppering strategies do not affect the password hashing function in any way.
The work factor is essentially the number of iterations of the hashing algorithm that are performed for each password (usually, it's actually 2^work iterations). The purpose of the work factor is to make calculating the hash more computationally expensive, which in turn reduces the speed and/or increases the cost for which an attacker can attempt to crack the password hash. The work factor is typically stored in the hash output.
When choosing a work factor, a balance needs to be struck between security and performance. Higher work factors will make the hashes more difficult for an attacker to crack but will also make the process of verifying a login attempt slower. If the work factor is too high, this may degrade the performance of the application and could also be used by an attacker to carry out a denial of service attack by making a large number of login attempts to exhaust the server's CPU.
The most common approach to upgrading the work factor is to wait until the user next authenticates and then to re-hash their password with the new work factor. This means that different hashes will have different work factors and may result in hashes never being upgraded if the user doesn't log back into the application. Depending on the application, it may be appropriate to remove the older password hashes and require users to reset their passwords next time they need to login in order to avoid storing older and less secure hashes.
There are a number of modern hashing algorithms that have been specifically designed for securely storing passwords. This means that they should be slow (unlike algorithms such as MD5 and SHA-1, which were designed to be fast), and how slow they are can be configured by changing the work factor.
Websites should not hide which password hashing algorithm they use. If you utilize a modern password hashing algorithm with proper configuration parameters, it should be safe to state in public which password hashing algorithms are in use and be listed here.
scrypt is a password-based key derivation function created by Colin Percival. While new systems should consider Argon2id for password hashing, scrypt should be configured properly when used in legacy systems.
bcrypt has a maximum length input length of 72 bytes for most implementations. To protect against this issue, a maximum password length of 72 bytes (or less if the implementation in use has smaller limits) should be enforced when using bcrypt.
An alternative approach is to pre-hash the user-supplied password with a fast algorithm such as SHA-256, and then to hash the resulting hash with bcrypt (i.e., bcrypt(base64(hmac-sha256(data:$password, key:$pepper)), $salt, $cost)). This is a dangerous (but common) practice that should be avoided due to password shucking and other issues when combining bcrypt with other hash functions. 2ff7e9595c
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