FC computing power
Publish: 2021-04-15 03:05:54
1. System maintenance
2. Kirin processor is the first domestic mobile phone processor. It is the proct of Hisilicon, a Huawei Company. At present, the performance of Kirin processor has surpassed that of MediaTek, which is approaching the processor of Qualcomm. Moreover, new procts are continuously developed and put on the market. The following is the schele of major events of Hisilicon:
1. In April 2015, Hisilicon released Kirin 935, It is mainly carried in Huawei P8 high configuration version and glory 7[ 2]
2. In 2015, in MWC, Hisilicon released a 64 bit 8-core chip, Hisilicon Qilin 930, which is carried on glory x2 and Huawei P8 (partial versions)
3. On December 3, 2014, Hisilicon released Kirin 620, a 64 bit 8-core chip, which is carried on the glory game 4x / 4C and Huawei P8 Youth Edition
4. On October 13, 2014, Hisilicon released Hisilicon Kirin 928 chip, which was carried on Huawei glory 6 supreme edition
5. On September 4, 2014, Hisilicon released super 8-core Hisilicon Kirin 925 chip, 4 arm A7 cores, 4 arm
A15 cores, plus a coprocessor, built-in baseband, supporting LTE cat. 6 standard network, carried on Huawei mate7 and glory 6plus
6. In June 2014, Hisilicon released the eight core Hisilicon Kirin 920 chip, which was launched on Huawei glory 6 in the same month
7. In May 2014, Hisilicon released the four core Kirin 910t, which was carried on Huawei P7
8. In February 2012, at the CES conference in Barcelona, Hisilicon released the four core mobile phone processor chip k3v2, and launched it with ascend
D.
1. In April 2015, Hisilicon released Kirin 935, It is mainly carried in Huawei P8 high configuration version and glory 7[ 2]
2. In 2015, in MWC, Hisilicon released a 64 bit 8-core chip, Hisilicon Qilin 930, which is carried on glory x2 and Huawei P8 (partial versions)
3. On December 3, 2014, Hisilicon released Kirin 620, a 64 bit 8-core chip, which is carried on the glory game 4x / 4C and Huawei P8 Youth Edition
4. On October 13, 2014, Hisilicon released Hisilicon Kirin 928 chip, which was carried on Huawei glory 6 supreme edition
5. On September 4, 2014, Hisilicon released super 8-core Hisilicon Kirin 925 chip, 4 arm A7 cores, 4 arm
A15 cores, plus a coprocessor, built-in baseband, supporting LTE cat. 6 standard network, carried on Huawei mate7 and glory 6plus
6. In June 2014, Hisilicon released the eight core Hisilicon Kirin 920 chip, which was launched on Huawei glory 6 in the same month
7. In May 2014, Hisilicon released the four core Kirin 910t, which was carried on Huawei P7
8. In February 2012, at the CES conference in Barcelona, Hisilicon released the four core mobile phone processor chip k3v2, and launched it with ascend
D.
3. How to calculate a met heart rate is not enough. This can't be calculated.
4. 6V × 37 + FC diameter 40mm, nominal tensile strength 1870mpa wire rope, wire rope minimum breaking force and wire breaking force sum should be what? How to calculate
GB8918-2006 important purpose wire rope
minimum breaking force of wire rope = 40 * 40 * 1870 * 0.36/1000 = 1077 (KN)
total breaking force of wire rope = 1.177 * minimum breaking force of wire rope = 1.177 * 1077 = 1267 (KN)
GB8918-2006 important purpose wire rope
minimum breaking force of wire rope = 40 * 40 * 1870 * 0.36/1000 = 1077 (KN)
total breaking force of wire rope = 1.177 * minimum breaking force of wire rope = 1.177 * 1077 = 1267 (KN)
5. 6x19 + fc-15.5mm, nominal tensile strength 1770mpa, minimum total breaking force of steel wire is 160.8kn, minimum breaking force of steel wire rope is 131.2kn. GB / t20118-2006 general purpose steel wire rope standard is adopted.
6.
C
the width of the beam section B = 200 mm, the height h = 450 mm, and the distance from the resultant force point of the compressive reinforcement to the near edge of the section A & # 39; S = 35mm
the distance from the resultant force point of tensile reinforcement to the near edge of the section is as = 35mm, the calculation span is l0 = 4860mm
the concrete strength grade is C40, the design value of longitudinal tensile reinforcement strength is FY = 360MPa, and the design value of longitudinal compressive reinforcement strength is F & # 39; Y = 360MPa,
non seismic design, the design section is located in the frame beam, the design bending moment M = 76.26kn · m, and the lower part of the section is under tension
extended data:
the quality of concrete is closely related to the type, amount and method of admixtures, which is also one of the important factors affecting the strength of concrete. The normal development of concrete strength can only be guaranteed under the suitable conditions of temperature and humidity, and it should be maintained according to the construction specifications. The temperature has a certain influence on the development of concrete strength
in summer, it is necessary to prevent exposure to the sun, and make full use of the time of high and low temperature in the morning and evening to pour concrete; The transportation and pouring time shall be shortened as far as possible to prevent sun exposure and increase the slump when the mixture is discharged from the tank; It is not suitable to water intermittently ring curing, because the temperature of concrete surface rises when it is dry, and it cools when it is watered. This alternating action of cold and heat will rece the strength and crack resistance of concrete. In winter, heat preservation and antifreeze are necessary. Now, comprehensive heat storage method and steam curing method are generally adopted in winter construction
7. It's not easy to calculate. There are many factors that can affect the cutting force
8. < p>" lt; img >" lt; &# 92; / img >" lt;/ p>" lt; p > < br/> Type of liquid pressure structure < / p>
9. The best way to protect the password is to use the salt password hashing. Hashing the password is a very simple thing, but many people make mistakes. Next, I hope to elaborate on how to hash the password properly and why
important reminder
if you're going to write your own code to hash your password, stop. It's too easy to make mistakes. This reminder applies to everyone, do not write their own password hash algorithm! There is a mature solution to save the password, that is to use phpass or the source code provided in this article
what is hash
hash (& quot; hello") = < br />hash(" hbllo") = < br />hash(" waltz") =
hash algorithm is a one-way function. It can convert any amount of data into a fixed length fingerprint, which is irreversible. And as long as the input changes, even if there is only one bit, the output hash value will be very different. This feature is just right for saving passwords. Because we want to use an irreversible algorithm to encrypt the saved password. At the same time, we need to verify whether the password is correct when the user logs in
in an account system using hash, the general process of user registration and authentication is as follows:
1, the user creates his own account
2, and the user password is stored in the database after hash operation. No plaintext password is stored on the server's hard disk
3. When the user logs in, the password entered by the user is hashed and compared with the password hash value saved in the database
4. If the hash value is exactly the same, the password entered by the user is considered correct. Otherwise, it is considered that the user has entered an invalid password
5. Repeat steps 3 and 4 each time the user tries to log in
in step 4, do not tell the user whether the account or password is wrong. Just display a general prompt, such as incorrect account or password. This prevents attackers from enumerating valid user names
it should also be noted that the hash function used to protect the password is not exactly the same as the hash function seen in the data structure class. For example, the hash function of hash table is designed to be fast, but not secure. Only cryptographic hash functions can be used to hash passwords. Such functions include sha256, SHA512, ripemd, whirlpool, etc
a common idea is that passwords are stored safely after hashing. This is obviously not true. There are many ways to quickly recover plaintext password from hash. Remember those MD5 cracking websites, you only need to submit a hash, and you can know the result in less than a second. Obviously, the simple hash of the password is far from our security requirements. In the next part, we will first discuss the common means to crack the password hash and obtain the plaintext< How to crack hash
dictionary and brute force attacks
the most common way to crack hash is to guess password. Then hash every possible password, compare the hash value of the password to be cracked with the hash value of the password to be guessed, if the two values are the same, then the password guessed before is the correct password plaintext. The common ways of guessing password attack are dictionary attack and violent attack< br />Dictionary Attack
Trying apple : failed
Trying blueberry : failed
Trying justinbeiber : failed
...
Trying letmein : failed
Trying s3cr3t : success!
dictionary attack is to put common passwords, words, phrases and other strings that may be used as passwords into a file, then hash each word in the file, and compare these hashes with the password hashes that need to be cracked. The success rate of this method depends on the size of the password dictionary and the suitability of the dictionary< br />Brute Force Attack
Trying aaaa : failed
Trying aaab : failed
Trying aaac : failed
...
Trying acdb : failed
Trying acdc : success!
a brute force attack is to try every possible character combination for a given password length. This method takes a lot of computer time. But in theory, as long as enough time, the final password will be able to crack out. But if the password is too long, it will take too long to crack
at present, there is no way to prevent dictionary attacks and violent attacks. We can only find ways to make them inefficient. If your password hash system is designed to be secure, then the only way to crack hash is to carry out dictionary or violent attack
lookup tables
for a specific hash type, if a large number of hashes need to be cracked, lookup table is a very effective and fast way. Its idea is to pre compute the hash of each password in the password dictionary. Then save the hash and the corresponding password in a table. A well-designed query table structure can query hundreds of hashes per second even if it stores billions of hashes
if you want to crack the hash by looking up the table, you can try to crack the following hash on the crashstation
reverse lookup tables
searching for hash (Apple) in users & #; hash list... : Matches [alice3, 0bob0, charles8]
Searching for hash(blueberry) in users' hash list... : Matches [usr10101, timmy, john91]
Searching for hash(letmein) in users' hash list... : Matches [wilson10, dragonslayerX, joe1984]
Searching for hash(s3cr3t) in users' hash list... : Matches [bruce19, knuth1337, john87]
Searching for hash( z@29hjja ) in users' Hash list...: no users used this password
this way allows attackers to attack a large number of hashes by dictionary and brute force attack without calculating a query table in advance
first of all, the attacker will create a user name and corresponding hash table according to the obtained database data. Then hash the common dictionary password and compare it with the hash of this table to know which users use this password. This kind of attack is very effective, because usually many users will use the same password<
rainbow tables
rainbow tables is a technology of exchanging space for time. It's very similar to table lookup cracking. It only sacrifices some cracking time to achieve the purpose of smaller storage space. Because rainbow table uses smaller storage space, unit space can store more hash. Rainbow table has been able to crack 8-bit length of any md5hash. The specific principle of rainbow table can be referred to http://www.project-rainbowcrack.com/
in the next chapter, we will discuss a technology called "salting". Through this technology, hash can not be cracked by looking up tables and rainbow tables
adding salt
hash & quot; hello") = < br />hash(" hello" + & quot; QxLUF1bgIAdeQX") = < br />hash(" hello" + & quot; bv5PehSMfV11Cd") = < br />hash(" hello" + & quot; YYLmfY6IehjZMQ") =
the way to look up tables and rainbow tables is effective because each password is hashed in the same way. If two users use the same password, their password hash must be the same. We can avoid this attack by randomizing each hash and getting different hashes from the same password twice
the specific operation is to add an immediate prefix or suffix to the password, and then hash it. The immediate suffix or prefix is "salt.". As shown in the example above, by adding salt, the same password is a completely different string every time it is hashed. We also need the salt to check whether the password entered by the user is correct, so the salt is usually saved in the database with hash, or as a part of hash string
Salt doesn't need to be kept secret, as long as the salt is random, look-up table and rainbow table will be invalid. Because the attacker can't know what salt is in advance, there is no way to calculate the query table and rainbow table in advance. If each user uses a different salt, the reverse table lookup attack will not succeed
in the next section, we will introce some common error implementations of salt
wrong way: short salt and salt reuse
the most common wrong implementation is that one salt is used in multiple hashes or the salt used is very short
Salt reuse
whether the salt is hard coded in the program or generated at random, using the same salt in each password hash will make this defense method invalid. Because the same password hash gets the same result twice. The attacker can use the reverse look-up table to carry out dictionary and violent attacks. Just add this fixed salt before hashing each password in the dictionary. If a popular program uses hard coded salt, then there may be query tables and rainbow tables for the salt of this program, so as to quickly crack the hash
every time a user creates or modifies a password, he must use a new random salt
short salt
if the number of bits of salt is too short, the attacker can also make a query table for all possible salts in advance. For example, there are 95x95x95 = 857375 possibilities for 3-bit ASCII character salt. It looks like a lot. If we make a 1MB query table with common password for each salt, 857375 salt is 837gb. Now it's only a few hundred yuan to buy a 1TB hard disk
for the same reason, never use a user name as salt. Although the user name may be different for each user, the user name is predictable and not completely random. Attackers can use common user names as salt to make query tables and rainbow tables to crack hash
according to some experience, the rule is that the size of salt should be consistent with the output of hash function. For example, the output of sha256 is 256 bits (32 bytes), and the length of salt should be 32 bytes of random data
wrong way: Double hash and odd hash functions
this section discusses another common misunderstanding of hash ciphers: odd combination of hash algorithms. People may solve the problem that combining different hash functions can make the data more secure. But in fact, the effect of this approach is very small. On the contrary, it may bring some interoperability problems, and even make hash more insecure sometimes. As mentioned at the beginning of this article, never try to write your own hash algorithm, but use the standard algorithm designed by experts. Some people think that using multiple hash functions can rece the speed of hash calculation and increase the difficulty of cracking. There is a better way to defend against attacks by slowing down hash computation, which will be described in detail below
here are some examples of weird hash function combinations found on the Internet< br />md5(sha1(password))
md5(
important reminder
if you're going to write your own code to hash your password, stop. It's too easy to make mistakes. This reminder applies to everyone, do not write their own password hash algorithm! There is a mature solution to save the password, that is to use phpass or the source code provided in this article
what is hash
hash (& quot; hello") = < br />hash(" hbllo") = < br />hash(" waltz") =
hash algorithm is a one-way function. It can convert any amount of data into a fixed length fingerprint, which is irreversible. And as long as the input changes, even if there is only one bit, the output hash value will be very different. This feature is just right for saving passwords. Because we want to use an irreversible algorithm to encrypt the saved password. At the same time, we need to verify whether the password is correct when the user logs in
in an account system using hash, the general process of user registration and authentication is as follows:
1, the user creates his own account
2, and the user password is stored in the database after hash operation. No plaintext password is stored on the server's hard disk
3. When the user logs in, the password entered by the user is hashed and compared with the password hash value saved in the database
4. If the hash value is exactly the same, the password entered by the user is considered correct. Otherwise, it is considered that the user has entered an invalid password
5. Repeat steps 3 and 4 each time the user tries to log in
in step 4, do not tell the user whether the account or password is wrong. Just display a general prompt, such as incorrect account or password. This prevents attackers from enumerating valid user names
it should also be noted that the hash function used to protect the password is not exactly the same as the hash function seen in the data structure class. For example, the hash function of hash table is designed to be fast, but not secure. Only cryptographic hash functions can be used to hash passwords. Such functions include sha256, SHA512, ripemd, whirlpool, etc
a common idea is that passwords are stored safely after hashing. This is obviously not true. There are many ways to quickly recover plaintext password from hash. Remember those MD5 cracking websites, you only need to submit a hash, and you can know the result in less than a second. Obviously, the simple hash of the password is far from our security requirements. In the next part, we will first discuss the common means to crack the password hash and obtain the plaintext< How to crack hash
dictionary and brute force attacks
the most common way to crack hash is to guess password. Then hash every possible password, compare the hash value of the password to be cracked with the hash value of the password to be guessed, if the two values are the same, then the password guessed before is the correct password plaintext. The common ways of guessing password attack are dictionary attack and violent attack< br />Dictionary Attack
Trying apple : failed
Trying blueberry : failed
Trying justinbeiber : failed
...
Trying letmein : failed
Trying s3cr3t : success!
dictionary attack is to put common passwords, words, phrases and other strings that may be used as passwords into a file, then hash each word in the file, and compare these hashes with the password hashes that need to be cracked. The success rate of this method depends on the size of the password dictionary and the suitability of the dictionary< br />Brute Force Attack
Trying aaaa : failed
Trying aaab : failed
Trying aaac : failed
...
Trying acdb : failed
Trying acdc : success!
a brute force attack is to try every possible character combination for a given password length. This method takes a lot of computer time. But in theory, as long as enough time, the final password will be able to crack out. But if the password is too long, it will take too long to crack
at present, there is no way to prevent dictionary attacks and violent attacks. We can only find ways to make them inefficient. If your password hash system is designed to be secure, then the only way to crack hash is to carry out dictionary or violent attack
lookup tables
for a specific hash type, if a large number of hashes need to be cracked, lookup table is a very effective and fast way. Its idea is to pre compute the hash of each password in the password dictionary. Then save the hash and the corresponding password in a table. A well-designed query table structure can query hundreds of hashes per second even if it stores billions of hashes
if you want to crack the hash by looking up the table, you can try to crack the following hash on the crashstation
reverse lookup tables
searching for hash (Apple) in users & #; hash list... : Matches [alice3, 0bob0, charles8]
Searching for hash(blueberry) in users' hash list... : Matches [usr10101, timmy, john91]
Searching for hash(letmein) in users' hash list... : Matches [wilson10, dragonslayerX, joe1984]
Searching for hash(s3cr3t) in users' hash list... : Matches [bruce19, knuth1337, john87]
Searching for hash( z@29hjja ) in users' Hash list...: no users used this password
this way allows attackers to attack a large number of hashes by dictionary and brute force attack without calculating a query table in advance
first of all, the attacker will create a user name and corresponding hash table according to the obtained database data. Then hash the common dictionary password and compare it with the hash of this table to know which users use this password. This kind of attack is very effective, because usually many users will use the same password<
rainbow tables
rainbow tables is a technology of exchanging space for time. It's very similar to table lookup cracking. It only sacrifices some cracking time to achieve the purpose of smaller storage space. Because rainbow table uses smaller storage space, unit space can store more hash. Rainbow table has been able to crack 8-bit length of any md5hash. The specific principle of rainbow table can be referred to http://www.project-rainbowcrack.com/
in the next chapter, we will discuss a technology called "salting". Through this technology, hash can not be cracked by looking up tables and rainbow tables
adding salt
hash & quot; hello") = < br />hash(" hello" + & quot; QxLUF1bgIAdeQX") = < br />hash(" hello" + & quot; bv5PehSMfV11Cd") = < br />hash(" hello" + & quot; YYLmfY6IehjZMQ") =
the way to look up tables and rainbow tables is effective because each password is hashed in the same way. If two users use the same password, their password hash must be the same. We can avoid this attack by randomizing each hash and getting different hashes from the same password twice
the specific operation is to add an immediate prefix or suffix to the password, and then hash it. The immediate suffix or prefix is "salt.". As shown in the example above, by adding salt, the same password is a completely different string every time it is hashed. We also need the salt to check whether the password entered by the user is correct, so the salt is usually saved in the database with hash, or as a part of hash string
Salt doesn't need to be kept secret, as long as the salt is random, look-up table and rainbow table will be invalid. Because the attacker can't know what salt is in advance, there is no way to calculate the query table and rainbow table in advance. If each user uses a different salt, the reverse table lookup attack will not succeed
in the next section, we will introce some common error implementations of salt
wrong way: short salt and salt reuse
the most common wrong implementation is that one salt is used in multiple hashes or the salt used is very short
Salt reuse
whether the salt is hard coded in the program or generated at random, using the same salt in each password hash will make this defense method invalid. Because the same password hash gets the same result twice. The attacker can use the reverse look-up table to carry out dictionary and violent attacks. Just add this fixed salt before hashing each password in the dictionary. If a popular program uses hard coded salt, then there may be query tables and rainbow tables for the salt of this program, so as to quickly crack the hash
every time a user creates or modifies a password, he must use a new random salt
short salt
if the number of bits of salt is too short, the attacker can also make a query table for all possible salts in advance. For example, there are 95x95x95 = 857375 possibilities for 3-bit ASCII character salt. It looks like a lot. If we make a 1MB query table with common password for each salt, 857375 salt is 837gb. Now it's only a few hundred yuan to buy a 1TB hard disk
for the same reason, never use a user name as salt. Although the user name may be different for each user, the user name is predictable and not completely random. Attackers can use common user names as salt to make query tables and rainbow tables to crack hash
according to some experience, the rule is that the size of salt should be consistent with the output of hash function. For example, the output of sha256 is 256 bits (32 bytes), and the length of salt should be 32 bytes of random data
wrong way: Double hash and odd hash functions
this section discusses another common misunderstanding of hash ciphers: odd combination of hash algorithms. People may solve the problem that combining different hash functions can make the data more secure. But in fact, the effect of this approach is very small. On the contrary, it may bring some interoperability problems, and even make hash more insecure sometimes. As mentioned at the beginning of this article, never try to write your own hash algorithm, but use the standard algorithm designed by experts. Some people think that using multiple hash functions can rece the speed of hash calculation and increase the difficulty of cracking. There is a better way to defend against attacks by slowing down hash computation, which will be described in detail below
here are some examples of weird hash function combinations found on the Internet< br />md5(sha1(password))
md5(
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