When you download a file in OS X, often the site issuing it may have a SHA (Secure Hash Algorithm) checksum listed, which you can use to verify the file. Checksums are a quick algorithm that takes select parts of a file and performs a quick computation on them (summing, multiplying, and otherwise combining them) that results in a number or code that should be unique to that file's contents. Since the sums are computed using data from all parts of the file, the sum is an indicator of file integrity, and can be used to verify the version … Read more
Disk Utility is Apple's tool for managing disks and disk images in OS X. One component of this program's image handling features is the ability to compute a checksum to verify the image's integrity. Sometimes when you download a disk image from a Web site, the site will mention a checksum for the image that you can compare to a locally computed checksum. If these do not match, then chances are the file was altered from the intended version supplied on the site.
There are a number of checksumming routines commonly used for providing integrity checks for … Read more
When you copy files from one location to another in OS X, the system should run a number of checks to validate the data and ensure that it was copied correctly; however, if you are using third-party utilities to copy a file, you might be concerned about potential corruption.
MacFixIt reader Douglas recently wrote in with such a concern.I was wondering if there is any way to verify a copy of files from one hard drive to another? I used SuperDuper to copy one of my RAIDs to another RAID; it was 7TB of stuff and took two days … Read more
Apple's Mac App Store, which was introduced in OS X 10.6.6, has become Apple's central location for distributing new software as well as managing updates to the OS and purchased applications. Though in most situations the Mac App Store works fine to download and run a specified installer, there are times when errors occur and even persist regardless of how many times you retry the download.
MacFixIt reader Silverio recently wrote in with such a problem:I've been experiencing problems to install updates for iMovie through Apple Store. The error message says that the product … Read more
Generally when a file you download is corrupted, opening it results in an error or just the inability to read it properly; however, in rare cases corruption in executable files such as installers and programs can result in crashes and other unwanted behavior.
Periodically files you download from online services such as the Mac App Store or from Web sites may become corrupted and result in a verification error when you try to open them. If this happens, then it is recommended you avoid using the file, since while usually it will just not read properly there are instances where … Read more
One problem that some people are having with the new Mac OS X Lion release is that the downloaded installer appears to be getting corrupted during the download process. After purchasing and downloading the installer, some find that the system will claim that the software cannot be verified after it has been launched.
Multiple users have confirmed that the MD5 checksum for the installer disk image is "b5d3753c62bfb69866e94dca9336a44a," and you can check this on your downloaded installer by running the following command in the Terminal (copy and paste it):
/sbin/md5 "/Applications/Install Mac OS X Lion.… Read more
Febooti fileTweak Hash & CRC sounds like the sort of place Indiana Jones ends up fighting his way out of, but it's actually a free hash and checksum calculator. Hash and checksum values are used to verify the integrity of large computer files by comparing special codes to see if anything has changed. That's a simple explanation of what many PC users see as a complicated and entirely too geeky procedure. It isn't a difficult concept, especially with free tools like Febooti at hand. To use the values the module creates, you can compare them with existing … Read more
Computers use checksums to check for data transmission errors; basically, they count the bits in a block of data and compare the number to a previously generated sum. If the two match, all is well; if not, something's gone wrong and it's time to look for data errors. Checksum verifiers are handy utilities that can scan software to verify its integrity. Marxio File Checksum Verifier calculates and verifies the checksums of programs downloaded from the Internet. It's free, compact, and portable, making it especially useful to system administrators and others who manage more than one machine.
This … Read more
MD5 Checksum Calculator is a bare-bones program for calculating and comparing MD5 files. While its layout leaves something to be desired, its results are fast and simple.
The program's interface is sparse, and the program offers no Help file or other instructions to guide users through its processes. Fortunately, some experimentation quickly produced a familiarity with the program's few command icons. You simply search a file tree to calculate your sum. Clicking on a specific file or program generates its MD5 sum, which is often used to check the integrity of files. MD5 Checksum Calculator can also compare … Read more
Cryptographic hash functions are commonly used to guard against malicious changes to protected data in a wide variety of software, Internet, and security applications, including digital signatures and other forms of authentication. Two of the most common cryptographic hash functions are the Secure Hash Algorithm (SHA) and Message Digest Algorithm-5 (MD5). Checksum utilities are used to verify the integrity of generated hashes. There are two basic types, those that calculate checksum values and those that also validate them by checking them against a list of values for the protected data, which is the only way it can be done. Raymond … Read more