This document discusses message authentication techniques including message encryption, message authentication codes (MACs), and hash functions. Message encryption provides authentication if symmetric encryption is used, but public key encryption only provides authentication if the sender also digitally signs the message. MACs provide assurance that a message was not altered and came from the sender by appending a cryptographic checksum. Hash functions condense messages to a fixed size in a way that makes finding collisions difficult. Both MACs and hash functions need to be sufficiently large, like 128 bits or more, to be secure against birthday and other attacks.
This material covers Authentication requirement, Authentication function, MAC, Hash function, Security of hash function and MAC, SHA, Digital signature and authentication protocols, DSS, Authentication protocols like Kerberos and X.509, entity authentication
This material covers Authentication requirement, Authentication function, MAC, Hash function, Security of hash function and MAC, SHA, Digital signature and authentication protocols, DSS, Authentication protocols like Kerberos and X.509, entity authentication
This material covers Authentication requirement, Authentication function, MAC, Hash function, Security of hash function and MAC, SHA, Digital signature and authentication protocols, DSS, Authentication protocols like Kerberos and X.509, entity authentication
This material covers Authentication requirement, Authentication function, MAC, Hash function, Security of hash function and MAC, SHA, Digital signature and authentication protocols, DSS, Authentication protocols like Kerberos and X.509, entity authentication
Information and network security 42 security of message authentication codeVaibhav Khanna
Message Authentication Requirements
Disclosure: Release of message contents to any person or process not possess- ing the appropriate cryptographic key.
Traffic analysis: Discovery of the pattern of traffic between parties. ...
Masquerade: Insertion of messages into the network from a fraudulent source
For a college course -- CNIT 141: Cryptography for Computer Networks, at City College San Francisco
Based on "Serious Cryptography: A Practical Introduction to Modern Encryption", by Jean-Philippe Aumasson, No Starch Press (November 6, 2017), ISBN-10: 1593278268 ISBN-13: 978-1593278267
Instructor: Sam Bowne
More info: https://samsclass.info/141/141_S19.shtml
Information and network security 41 message authentication codeVaibhav Khanna
In cryptography, a message authentication code, sometimes known as a tag, is a short piece of information used to authenticate a message—in other words, to confirm that the message came from the stated sender and has not been changed.
Using recycled concrete aggregates (RCA) for pavements is crucial to achieving sustainability. Implementing RCA for new pavement can minimize carbon footprint, conserve natural resources, reduce harmful emissions, and lower life cycle costs. Compared to natural aggregate (NA), RCA pavement has fewer comprehensive studies and sustainability assessments.
Welcome to WIPAC Monthly the magazine brought to you by the LinkedIn Group Water Industry Process Automation & Control.
In this month's edition, along with this month's industry news to celebrate the 13 years since the group was created we have articles including
A case study of the used of Advanced Process Control at the Wastewater Treatment works at Lleida in Spain
A look back on an article on smart wastewater networks in order to see how the industry has measured up in the interim around the adoption of Digital Transformation in the Water Industry.
Information and network security 42 security of message authentication codeVaibhav Khanna
Message Authentication Requirements
Disclosure: Release of message contents to any person or process not possess- ing the appropriate cryptographic key.
Traffic analysis: Discovery of the pattern of traffic between parties. ...
Masquerade: Insertion of messages into the network from a fraudulent source
For a college course -- CNIT 141: Cryptography for Computer Networks, at City College San Francisco
Based on "Serious Cryptography: A Practical Introduction to Modern Encryption", by Jean-Philippe Aumasson, No Starch Press (November 6, 2017), ISBN-10: 1593278268 ISBN-13: 978-1593278267
Instructor: Sam Bowne
More info: https://samsclass.info/141/141_S19.shtml
Information and network security 41 message authentication codeVaibhav Khanna
In cryptography, a message authentication code, sometimes known as a tag, is a short piece of information used to authenticate a message—in other words, to confirm that the message came from the stated sender and has not been changed.
Using recycled concrete aggregates (RCA) for pavements is crucial to achieving sustainability. Implementing RCA for new pavement can minimize carbon footprint, conserve natural resources, reduce harmful emissions, and lower life cycle costs. Compared to natural aggregate (NA), RCA pavement has fewer comprehensive studies and sustainability assessments.
Welcome to WIPAC Monthly the magazine brought to you by the LinkedIn Group Water Industry Process Automation & Control.
In this month's edition, along with this month's industry news to celebrate the 13 years since the group was created we have articles including
A case study of the used of Advanced Process Control at the Wastewater Treatment works at Lleida in Spain
A look back on an article on smart wastewater networks in order to see how the industry has measured up in the interim around the adoption of Digital Transformation in the Water Industry.
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Immunizing Image Classifiers Against Localized Adversary Attacksgerogepatton
This paper addresses the vulnerability of deep learning models, particularly convolutional neural networks
(CNN)s, to adversarial attacks and presents a proactive training technique designed to counter them. We
introduce a novel volumization algorithm, which transforms 2D images into 3D volumetric representations.
When combined with 3D convolution and deep curriculum learning optimization (CLO), itsignificantly improves
the immunity of models against localized universal attacks by up to 40%. We evaluate our proposed approach
using contemporary CNN architectures and the modified Canadian Institute for Advanced Research (CIFAR-10
and CIFAR-100) and ImageNet Large Scale Visual Recognition Challenge (ILSVRC12) datasets, showcasing
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Understanding Inductive Bias in Machine LearningSUTEJAS
This presentation explores the concept of inductive bias in machine learning. It explains how algorithms come with built-in assumptions and preferences that guide the learning process. You'll learn about the different types of inductive bias and how they can impact the performance and generalizability of machine learning models.
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By understanding inductive bias, you can gain valuable insights into how machine learning models work and make informed decisions when building and deploying them.
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Heap sort is a comparison-based sorting technique based on Binary Heap data structure. It is similar to the selection sort where we first find the minimum element and place the minimum element at the beginning. Repeat the same process for the remaining elements.
We have compiled the most important slides from each speaker's presentation. This year’s compilation, available for free, captures the key insights and contributions shared during the DfMAy 2024 conference.
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2. Chapter 11 – Message
Authentication and Hash
Functions
At cats' green on the Sunday he took the message from
the inside of the pillar and added Peter Moran's name to
the two names already printed there in the "Brontosaur"
code. The message now read: “Leviathan to Dragon:
Martin Hillman, Trevor Allan, Peter Moran: observe and
tail.” What was the good of it John hardly knew. He felt
better, he felt that at last he had made an attack on Peter
Moran instead of waiting passively and effecting no
retaliation. Besides, what was the use of being in
possession of the key to the codes if he never took
advantage of it?
—Talking to Strange Men, Ruth Rendell
3. Message Authentication
message authentication is concerned with:
protecting the integrity of a message
validating identity of originator
non-repudiation of origin (dispute resolution)
will consider the security requirements
then three alternative functions used:
message encryption
message authentication code (MAC)
hash function
5. Message Encryption
message encryption by itself also provides
a measure of authentication
if symmetric encryption is used then:
receiver know sender must have created it
since only sender and receiver now key used
know content cannot of been altered
if message has suitable structure, redundancy
or a checksum to detect any changes
6. Message Encryption
if public-key encryption is used:
encryption provides no confidence of sender
since anyone potentially knows public-key
however if
• sender signs message using their private-key
• then encrypts with recipients public key
• have both secrecy and authentication
again need to recognize corrupted messages
but at cost of two public-key uses on message
7. Message Authentication Code
(MAC)
generated by an algorithm that creates a
small fixed-sized block
depending on both message and some key
like encryption though need not be reversible
appended to message as a signature
receiver performs same computation on
message and checks it matches the MAC
provides assurance that message is
unaltered and comes from sender
9. Message Authentication
Codes
as shown the MAC provides authentication
can also use encryption for secrecy
generally use separate keys for each
can compute MAC either before or after encryption
is generally regarded as better done before
why use a MAC?
sometimes only authentication is needed
sometimes need authentication to persist longer than
the encryption (eg. archival use)
note that a MAC is not a digital signature
10. MAC Properties
a MAC is a cryptographic checksum
MAC = CK(M)
condenses a variable-length message M
using a secret key K
to a fixed-sized authenticator
is a many-to-one function
potentially many messages have same MAC
but finding these needs to be very difficult
11. Requirements for MACs
taking into account the types of attacks
need the MAC to satisfy the following:
1. knowing a message and MAC, is infeasible
to find another message with same MAC
2. MACs should be uniformly distributed
3. MAC should depend equally on all bits of the
message
12. Using Symmetric Ciphers for
MACs
can use any block cipher chaining mode
and use final block as a MAC
Data Authentication Algorithm (DAA) is
a widely used MAC based on DES-CBC
using IV=0 and zero-pad of final block
encrypt message using DES in CBC mode
and send just the final block as the MAC
• or the leftmost M bits (16≤M≤64) of final block
but final MAC is now too small for security
14. Hash Functions
condenses arbitrary message to fixed size
h = H(M)
usually assume that the hash function is
public and not keyed
cf. MAC which is keyed
hash used to detect changes to message
can use in various ways with message
most often to create a digital signature
16. Requirements for Hash
Functions
1. can be applied to any sized message M
2. produces fixed-length output h
3. is easy to compute h=H(M) for any message M
4. given h is infeasible to find x s.t. H(x)=h
• one-way property
5. given x is infeasible to find y s.t. H(y)=H(x)
• weak collision resistance
6. is infeasible to find any x,y s.t. H(y)=H(x)
• strong collision resistance
17. Simple Hash Functions
are several proposals for simple functions
based on XOR of message blocks
not secure since can manipulate any
message and either not change hash or
change hash also
need a stronger cryptographic function
(next chapter)
18. Birthday Attacks
might think a 64-bit hash is secure
but by Birthday Paradox is not
birthday attack works thus:
opponent generates 2
m/2 variations of a valid message
all with essentially the same meaning
opponent also generates 2
m/2 variations of a desired
fraudulent message
two sets of messages are compared to find pair with
same hash (probability > 0.5 by birthday paradox)
have user sign the valid message, then substitute the
forgery which will have a valid signature
conclusion is that need to use larger MAC/hash
19. Block Ciphers as Hash
Functions
can use block ciphers as hash functions
using H0=0 and zero-pad of final block
compute: Hi = EMi
[Hi-1]
and use final block as the hash value
similar to CBC but without a key
resulting hash is too small (64-bit)
both due to direct birthday attack
and to “meet-in-the-middle” attack
other variants also susceptible to attack
20. Hash Functions & MAC
Security
like block ciphers have:
brute-force attacks exploiting
strong collision resistance hash have cost 2
m/2
• have proposal for h/w MD5 cracker
• 128-bit hash looks vulnerable, 160-bits better
MACs with known message-MAC pairs
• can either attack keyspace (cf key search) or MAC
• at least 128-bit MAC is needed for security
21. Hash Functions & MAC
Security
cryptanalytic attacks exploit structure
like block ciphers want brute-force attacks to be the
best alternative
have a number of analytic attacks on iterated
hash functions
CVi = f[CVi-1, Mi]; H(M)=CVN
typically focus on collisions in function f
like block ciphers is often composed of rounds
attacks exploit properties of round functions
22. Summary
have considered:
message authentication using
message encryption
MACs
hash functions
general approach & security