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The Use of Hashed PasswordsA widely
The Use of Hashed Passwords
A widely used password security technique is the use of hashed passwords and a salt
value. This scheme is found on virtually all UNIX variants as well as on a number
of other operating systems. The following procedure is employed ( Figure 3.1a ). To
load a new password into the system, the user selects or is assigned a password. This
password is combined with a fixed-length salt value [MORR79]. In older implementations,
this value is related to the time at which the password is assigned to the user.
Newer implementations use a pseudorandom or random number. The password
and salt serve as inputs to a hashing algorithm to produce a fixed-length hash code.
The hash algorithm is designed to be slow to execute to thwart attacks. The hashed
password is then stored, together with a plaintext copy of the salt, in the password
file for the corresponding user ID. The hashed-password method has been shown to
be secure against a variety of cryptanalytic attacks [WAGN00].
When a user attempts to log on to a UNIX system, the user provides an ID
and a password (Figure 3.1b). The operating system uses the ID to index into the
password file and retrieve the plaintext salt and the encrypted password. The salt
and user-supplied password are used as input to the encryption routine. If the result
matches the stored value, the password is accepted.
The salt serves three purposes:
• It prevents duplicate passwords from being visible in the password file. Even if
two users choose the same password, those passwords will be assigned different
salt values. Hence, the hashed passwords of the two users will differ.
• It greatly increases the difficulty of offline dictionary attacks. For a salt of
length b bits, the number of possible passwords is increased by a factor of 2b,
increasing the difficulty of guessing a password in a dictionary attack.
• It becomes nearly impossible to find out whether a person with passwords on
two or more systems has used the same password on all of them.
A widely used password security technique is the use of hashed passwords and a salt
value. This scheme is found on virtually all UNIX variants as well as on a number
of other operating systems. The following procedure is employed ( Figure 3.1a ). To
load a new password into the system, the user selects or is assigned a password. This
password is combined with a fixed-length salt value [MORR79]. In older implementations,
this value is related to the time at which the password is assigned to the user.
Newer implementations use a pseudorandom or random number. The password
and salt serve as inputs to a hashing algorithm to produce a fixed-length hash code.
The hash algorithm is designed to be slow to execute to thwart attacks. The hashed
password is then stored, together with a plaintext copy of the salt, in the password
file for the corresponding user ID. The hashed-password method has been shown to
be secure against a variety of cryptanalytic attacks [WAGN00].
When a user attempts to log on to a UNIX system, the user provides an ID
and a password (Figure 3.1b). The operating system uses the ID to index into the
password file and retrieve the plaintext salt and the encrypted password. The salt
and user-supplied password are used as input to the encryption routine. If the result
matches the stored value, the password is accepted.
The salt serves three purposes:
• It prevents duplicate passwords from being visible in the password file. Even if
two users choose the same password, those passwords will be assigned different
salt values. Hence, the hashed passwords of the two users will differ.
• It greatly increases the difficulty of offline dictionary attacks. For a salt of
length b bits, the number of possible passwords is increased by a factor of 2b,
increasing the difficulty of guessing a password in a dictionary attack.
• It becomes nearly impossible to find out whether a person with passwords on
two or more systems has used the same password on all of them.
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Menggunakan sandi yang terpotongTeknik keamanan password yang digunakan adalah menggunakan password yang terpotong dan garamnilai. Skema ini ditemukan pada hampir semua varian UNIX serta sejumlahsistem operasi lain. Prosedur berikut yang digunakan (gambar 3.1a). Untukmemuat kata sandi baru ke dalam sistem, pengguna memilih atau diberikan sandi. Inisandi dikombinasikan dengan nilai garam tetap panjang [MORR79]. Dalam implementasi yang lebih tua,nilai ini berkaitan dengan waktu di mana password ditetapkan ke pengguna.Implementasi baru menggunakan angka pseudorandom atau acak. Passworddan garam berfungsi sebagai masukan untuk hashing algoritma untuk menghasilkan kode hash tetap panjang.Algoritma hash dirancang untuk menjadi lambat untuk mengeksekusi untuk menggagalkan serangan. Terpotongsandi kemudian disimpan, bersama dengan salinan plaintext garam, sandifile untuk ID pengguna yang sesuai. Metode hashed-password telah terbuktiakan aman terhadap berbagai serangan cryptanalytic [WAGN00].Ketika pengguna mencoba untuk log on ke sebuah sistem UNIX, pengguna memberikan IDdan password (gambar 3.1b). Sistem operasi menggunakan ID untuk indeks kepassword file dan mengambil garam plaintext dan sandi yang dienkripsi. Garamdan password yang diberikan pengguna-digunakan sebagai masukan untuk enkripsi rutin. Jika hasilpertandingan nilai tersimpan, password yang diterima.Garam menyajikan tiga tujuan:• Mencegah duplikat password tidak terlihat dalam file sandi. Bahkan jikadua pengguna memilih password yang sama, password tersebut akan dapat ditetapkan berbedanilai-nilai garam. Oleh karena itu, password terpotong dua pengguna akan berbeda.• Ini sangat meningkatkan kesulitan dalam serangan kamus offline. Untuk garampanjang b bit, jumlah sandi mungkin meningkat dengan faktor 2b,meningkatkan kesulitan untuk menebak password dalam serangan Kamus.• Menjadi hampir mustahil untuk mengetahui apakah seseorang dengan sandi padadua atau lebih sistem telah menggunakan password yang sama pada mereka semua.
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The Use of Hashed Passwords
A widely used password security technique is the use of hashed passwords and a salt
value. This scheme is found on virtually all UNIX variants as well as on a number
of other operating systems. The following procedure is employed ( Figure 3.1a ). To
load a new password into the system, the user selects or is assigned a password. This
password is combined with a fixed-length salt value [MORR79]. In older implementations,
this value is related to the time at which the password is assigned to the user.
Newer implementations use a pseudorandom or random number. The password
and salt serve as inputs to a hashing algorithm to produce a fixed-length hash code.
The hash algorithm is designed to be slow to execute to thwart attacks. The hashed
password is then stored, together with a plaintext copy of the salt, in the password
file for the corresponding user ID. The hashed-password method has been shown to
be secure against a variety of cryptanalytic attacks [WAGN00].
When a user attempts to log on to a UNIX system, the user provides an ID
and a password (Figure 3.1b). The operating system uses the ID to index into the
password file and retrieve the plaintext salt and the encrypted password. The salt
and user-supplied password are used as input to the encryption routine. If the result
matches the stored value, the password is accepted.
The salt serves three purposes:
• It prevents duplicate passwords from being visible in the password file. Even if
two users choose the same password, those passwords will be assigned different
salt values. Hence, the hashed passwords of the two users will differ.
• It greatly increases the difficulty of offline dictionary attacks. For a salt of
length b bits, the number of possible passwords is increased by a factor of 2b,
increasing the difficulty of guessing a password in a dictionary attack.
• It becomes nearly impossible to find out whether a person with passwords on
two or more systems has used the same password on all of them.
A widely used password security technique is the use of hashed passwords and a salt
value. This scheme is found on virtually all UNIX variants as well as on a number
of other operating systems. The following procedure is employed ( Figure 3.1a ). To
load a new password into the system, the user selects or is assigned a password. This
password is combined with a fixed-length salt value [MORR79]. In older implementations,
this value is related to the time at which the password is assigned to the user.
Newer implementations use a pseudorandom or random number. The password
and salt serve as inputs to a hashing algorithm to produce a fixed-length hash code.
The hash algorithm is designed to be slow to execute to thwart attacks. The hashed
password is then stored, together with a plaintext copy of the salt, in the password
file for the corresponding user ID. The hashed-password method has been shown to
be secure against a variety of cryptanalytic attacks [WAGN00].
When a user attempts to log on to a UNIX system, the user provides an ID
and a password (Figure 3.1b). The operating system uses the ID to index into the
password file and retrieve the plaintext salt and the encrypted password. The salt
and user-supplied password are used as input to the encryption routine. If the result
matches the stored value, the password is accepted.
The salt serves three purposes:
• It prevents duplicate passwords from being visible in the password file. Even if
two users choose the same password, those passwords will be assigned different
salt values. Hence, the hashed passwords of the two users will differ.
• It greatly increases the difficulty of offline dictionary attacks. For a salt of
length b bits, the number of possible passwords is increased by a factor of 2b,
increasing the difficulty of guessing a password in a dictionary attack.
• It becomes nearly impossible to find out whether a person with passwords on
two or more systems has used the same password on all of them.
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- 91.1 Computer Security ConceptsA Definit
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- READER’S AND INSTRUCTOR’SGUIDE
- Gutten Morgen My Mooad boster
- READER’S AND INSTRUCTOR’SGUIDE
- Selamat pagi sayang selamat menjalankan
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- COMPUTER SECURITY CONCEPTS
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- • Confidentiality: This term covers two
- Computer Security: The protection afford
- Pasti
- • Confidentiality: This term covers two
- Pesan
- OVERVIEW
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- 1.1 Computer Security ConceptsA Definiti
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- LEARNING OBJECTIVESAfter studying this c
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- This chapter provides an overview of com
