Billy Chandler

Billy Chandler

1572576598

Getting Your Hands Dirty with TensorFlow 2.0 and Keras API

Diving into technical details of the regression model creation with TensorFlow 2.0 and Keras API. In TensorFlow 2.0, Keras comes out of the box with TensorFlow library. API is simplified and more convenient to use.

TensorFlow 2.0 comes with Keras packaged inside, there is no need to import Keras as a separate module (although you can do this if you need). TensorFlow 2.0 API is simplified and improved. This is good news for us — Machine Learning developers.

This is how you import Keras now, from TensorFlow:

from tensorflow import feature_column
from tensorflow import keras
from tensorflow.keras import layersprint(tf.__version__)
2.0.0

I’m using tf.data input pipeline to encode categorical columns, Keras API works well with tf.data. One of the main advantages of tf.data is the fact that it acts as a bridge between data and model. There is no need to transform data by yourself, enough to define transformation rule — transformed data automatically will be applied during training.

Data is fetched from CSV file into Pandas dataframe:

column_names = ['report_id','report_params','day_part','exec_time']
raw_dataframe = pd.read_csv('report_exec_times.csv')
dataframe = raw_dataframe.copy()dataframe.head()

Column values for report_params vary, we need to normalize this column (make values to be on a similar scale):

eps=0.001 # 0 => 0.1¢
dataframe['report_params'] = np.log(dataframe.pop('report_params')+eps)

I’m using a utility method (this method is taken from TensorFlow tutorial) to create tf.data dataset from Pandas dataframe:

def df_to_dataset(dataframe, shuffle=True, batch_size=32):
  dataframe = dataframe.copy()
  labels = dataframe.pop('exec_time')
  ds = tf.data.Dataset.from_tensor_slices((dict(dataframe), labels))
  if shuffle:
    ds = ds.shuffle(buffer_size=len(dataframe))
  ds = ds.batch(batch_size)
  return ds

Next, we need to define data mapping for categorical columns encoding. I’m using TensorFlow vocabulary list function, including mapping for all unique values (if there are many values, it would be better to use embedding API). Two columns are encoded — report_id and day_part:

feature_columns = []feature_columns.append(feature_column.numeric_column('report_params'))report_id = feature_column.categorical_column_with_vocabulary_list('report_id', ['1', '2', '3', '4', '5'])
report_id_one_hot = feature_column.indicator_column(report_id)
feature_columns.append(report_id_one_hot)day_part = feature_column.categorical_column_with_vocabulary_list('day_part', ['1', '2', '3'])
day_part_one_hot = feature_column.indicator_column(day_part)
feature_columns.append(day_part_one_hot)

Create Keras dense features layer out of array with TensorFlow encodings. We will use this layer during Keras model construction to define model training features:

feature_layer = tf.keras.layers.DenseFeatures(feature_columns)

We are done with features. Next, convert Pandas dataframe to tf.data with the help of utility function:

batch_size = 32
train_ds = df_to_dataset(train, batch_size=batch_size)
val_ds = df_to_dataset(val, shuffle=False, batch_size=batch_size)
test_ds = df_to_dataset(test, shuffle=False, batch_size=batch_size)

Dense features layer is used when Keras sequential model is defined (there is no need to pass array of features later into a fit function):

def build_model(feature_layer):
  model = keras.Sequential([
    feature_layer,
    layers.Dense(16, activation='relu'),
    layers.Dense(16, activation='relu'),
    layers.Dense(1)
  ])  optimizer = keras.optimizers.RMSprop(0.001)  model.compile(loss='mse',
                optimizer=optimizer,
                metrics=['mae', 'mse'])
  return model

Training is executed through model.fit function. We are using tf.data input pipeline to pass training and validation sets:

history = model.fit(train_ds,
              validation_data=val_ds,
              epochs=EPOCHS,
              callbacks=[early_stop])

The awesome thing about it — data encoding happens behind the scenes, based on the rules defined for the feature layer.

How to run model.predict function with tf.data and feature layer? It’s simple.

Construct Pandas dataframe with input data:

headers = ['report_id', 'report_params', 'day_part']
dataframe_input = pd.DataFrame([[1, 15, 3]],
                                columns=headers, 
                                dtype=float,
                                index=['input'])

Convert report_params value to be on the same scale as it was for the training:

eps=0.001 # 0 => 0.1¢
dataframe_input['report_params'] = np.log(dataframe_input.pop('report_params')+eps)

Create tf.data input pipeline out of Pandas dataframe:

input_ds = tf.data.Dataset.from_tensor_slices(dict(dataframe_input))
input_ds = input_ds.batch(1)

Run model.predict function:

res = model.predict(input_ds)
print(res)

Resources:

  • Source code with sample data is available on my GitHub repo

Enjoy !

#TensorFlow #Keras #python #machine-learning

What is GEEK

Buddha Community

Getting Your Hands Dirty with TensorFlow 2.0 and Keras API
최 호민

최 호민

1642390128

파이썬 코딩 무료 강의 - 이미지 처리, 얼굴 인식을 통한 캐릭터 씌우기를 해보아요

파이썬 코딩 무료 강의 (활용편6) - 이미지 처리, 얼굴 인식을 통한 캐릭터 씌우기를 해보아요

파이썬 무료 강의 (활용편6 - 이미지 처리)입니다.
OpenCV 를 이용한 다양한 이미지 처리 기법과 재미있는 프로젝트를 진행합니다.
누구나 볼 수 있도록 쉽고 재미있게 제작하였습니다. ^^

[소개]
(0:00:00) 0.Intro
(0:00:31) 1.소개
(0:02:18) 2.활용편 6 이미지 처리 소개

[OpenCV 전반전]
(0:04:36) 3.환경설정
(0:08:41) 4.이미지 출력
(0:21:51) 5.동영상 출력 #1 파일
(0:29:58) 6.동영상 출력 #2 카메라
(0:34:23) 7.도형 그리기 #1 빈 스케치북
(0:39:49) 8.도형 그리기 #2 영역 색칠
(0:42:26) 9.도형 그리기 #3 직선
(0:51:23) 10.도형 그리기 #4 원
(0:55:09) 11.도형 그리기 #5 사각형
(0:58:32) 12.도형 그리기 #6 다각형
(1:09:23) 13.텍스트 #1 기본
(1:17:45) 14.텍스트 #2 한글 우회
(1:24:14) 15.파일 저장 #1 이미지
(1:29:27) 16.파일 저장 #2 동영상
(1:39:29) 17.크기 조정
(1:50:16) 18.이미지 자르기
(1:57:03) 19.이미지 대칭
(2:01:46) 20.이미지 회전
(2:06:07) 21.이미지 변형 - 흑백
(2:11:25) 22.이미지 변형 - 흐림
(2:18:03) 23.이미지 변형 - 원근 #1
(2:27:45) 24.이미지 변형 - 원근 #2

[반자동 문서 스캐너 프로젝트]
(2:32:50) 25.미니 프로젝트 1 - #1 마우스 이벤트 등록
(2:42:06) 26.미니 프로젝트 1 - #2 기본 코드 완성
(2:49:54) 27.미니 프로젝트 1 - #3 지점 선 긋기
(2:55:24) 28.미니 프로젝트 1 - #4 실시간 선 긋기

[OpenCV 후반전]
(3:01:52) 29.이미지 변형 - 이진화 #1 Trackbar
(3:14:37) 30.이미지 변형 - 이진화 #2 임계값
(3:20:26) 31.이미지 변형 - 이진화 #3 Adaptive Threshold
(3:28:34) 32.이미지 변형 - 이진화 #4 오츠 알고리즘
(3:32:22) 33.이미지 변환 - 팽창
(3:41:10) 34.이미지 변환 - 침식
(3:45:56) 35.이미지 변환 - 열림 & 닫힘
(3:54:10) 36.이미지 검출 - 경계선
(4:05:08) 37.이미지 검출 - 윤곽선 #1 기본
(4:15:26) 38.이미지 검출 - 윤곽선 #2 찾기 모드
(4:20:46) 39.이미지 검출 - 윤곽선 #3 면적

[카드 검출 & 분류기 프로젝트]
(4:27:42) 40.미니프로젝트 2

[퀴즈]
(4:31:57) 41.퀴즈

[얼굴인식 프로젝트]
(4:41:25) 42.환경설정 및 기본 코드 정리
(4:54:48) 43.눈과 코 인식하여 도형 그리기
(5:10:42) 44.그림판 이미지 씌우기
(5:20:52) 45.캐릭터 이미지 씌우기
(5:33:10) 46.보충설명
(5:40:53) 47.마치며 (학습 참고 자료)
(5:42:18) 48.Outro


[학습자료]
수업에 필요한 이미지, 동영상 자료 링크입니다.

고양이 이미지 : https://pixabay.com/images/id-2083492/ 
크기 : 640 x 390  
파일명 : img.jpg

고양이 동영상 : https://www.pexels.com/video/7515833/ 
크기 : SD (360 x 640)  
파일명 : video.mp4

신문 이미지 : https://pixabay.com/images/id-350376/ 
크기 : 1280 x 853  
파일명 : newspaper.jpg

카드 이미지 1 : https://pixabay.com/images/id-682332/ 
크기 : 1280 x 1019  
파일명 : poker.jpg

책 이미지 : https://www.pexels.com/photo/1029807/ 
크기 : Small (640 x 853)  
파일명 : book.jpg

눈사람 이미지 : https://pixabay.com/images/id-1300089/ 
크기 : 1280 x 904  
파일명 : snowman.png

카드 이미지 2 : https://pixabay.com/images/id-161404/ 
크기 : 640 x 408  
파일명 : card.png

퀴즈용 동영상 : https://www.pexels.com/video/3121459/ 
크기 : HD (1280 x 720)  
파일명 : city.mp4

프로젝트용 동영상 : https://www.pexels.com/video/3256542/ 
크기 : Full HD (1920 x 1080)  
파일명 : face_video.mp4

프로젝트용 캐릭터 이미지 : https://www.freepik.com/free-vector/cute-animal-masks-video-chat-application-effect-filters-set_6380101.htm  
파일명 : right_eye.png (100 x 100), left_eye.png (100 x 100), nose.png (300 x 100)

무료 이미지 편집 도구 : https://pixlr.com/kr/
(Pixlr E -Advanced Editor)

#python #opencv 

Semantic Similarity Framework for Knowledge Graph

Introduction

Sematch is an integrated framework for the development, evaluation, and application of semantic similarity for Knowledge Graphs (KGs). It is easy to use Sematch to compute semantic similarity scores of concepts, words and entities. Sematch focuses on specific knowledge-based semantic similarity metrics that rely on structural knowledge in taxonomy (e.g. depth, path length, least common subsumer), and statistical information contents (corpus-IC and graph-IC). Knowledge-based approaches differ from their counterpart corpus-based approaches relying on co-occurrence (e.g. Pointwise Mutual Information) or distributional similarity (Latent Semantic Analysis, Word2Vec, GLOVE and etc). Knowledge-based approaches are usually used for structural KGs, while corpus-based approaches are normally applied in textual corpora.

In text analysis applications, a common pipeline is adopted in using semantic similarity from concept level, to word and sentence level. For example, word similarity is first computed based on similarity scores of WordNet concepts, and sentence similarity is computed by composing word similarity scores. Finally, document similarity could be computed by identifying important sentences, e.g. TextRank.

logo

KG based applications also meet similar pipeline in using semantic similarity, from concept similarity (e.g. http://dbpedia.org/class/yago/Actor109765278) to entity similarity (e.g. http://dbpedia.org/resource/Madrid). Furthermore, in computing document similarity, entities are extracted and document similarity is computed by composing entity similarity scores.

kg

In KGs, concepts usually denote ontology classes while entities refer to ontology instances. Moreover, those concepts are usually constructed into hierarchical taxonomies, such as DBpedia ontology class, thus quantifying concept similarity in KG relies on similar semantic information (e.g. path length, depth, least common subsumer, information content) and semantic similarity metrics (e.g. Path, Wu & Palmer,Li, Resnik, Lin, Jiang & Conrad and WPath). In consequence, Sematch provides an integrated framework to develop and evaluate semantic similarity metrics for concepts, words, entities and their applications.


Getting started: 20 minutes to Sematch

Install Sematch

You need to install scientific computing libraries numpy and scipy first. An example of installing them with pip is shown below.

pip install numpy scipy

Depending on different OS, you can use different ways to install them. After sucessful installation of numpy and scipy, you can install sematch with following commands.

pip install sematch
python -m sematch.download

Alternatively, you can use the development version to clone and install Sematch with setuptools. We recommend you to update your pip and setuptools.

git clone https://github.com/gsi-upm/sematch.git
cd sematch
python setup.py install

We also provide a Sematch-Demo Server. You can use it for experimenting with main functionalities or take it as an example for using Sematch to develop applications. Please check our Documentation for more details.

Computing Word Similarity

The core module of Sematch is measuring semantic similarity between concepts that are represented as concept taxonomies. Word similarity is computed based on the maximum semantic similarity of WordNet concepts. You can use Sematch to compute multi-lingual word similarity based on WordNet with various of semantic similarity metrics.

from sematch.semantic.similarity import WordNetSimilarity
wns = WordNetSimilarity()

# Computing English word similarity using Li method
wns.word_similarity('dog', 'cat', 'li') # 0.449327301063
# Computing Spanish word similarity using Lin method
wns.monol_word_similarity('perro', 'gato', 'spa', 'lin') #0.876800984373
# Computing Chinese word similarity using  Wu & Palmer method
wns.monol_word_similarity('狗', '猫', 'cmn', 'wup') # 0.857142857143
# Computing Spanish and English word similarity using Resnik method
wns.crossl_word_similarity('perro', 'cat', 'spa', 'eng', 'res') #7.91166650904
# Computing Spanish and Chinese word similarity using Jiang & Conrad method
wns.crossl_word_similarity('perro', '猫', 'spa', 'cmn', 'jcn') #0.31023804699
# Computing Chinese and English word similarity using WPath method
wns.crossl_word_similarity('狗', 'cat', 'cmn', 'eng', 'wpath')#0.593666388463

Computing semantic similarity of YAGO concepts.

from sematch.semantic.similarity import YagoTypeSimilarity
sim = YagoTypeSimilarity()

#Measuring YAGO concept similarity through WordNet taxonomy and corpus based information content
sim.yago_similarity('http://dbpedia.org/class/yago/Dancer109989502','http://dbpedia.org/class/yago/Actor109765278', 'wpath') #0.642
sim.yago_similarity('http://dbpedia.org/class/yago/Dancer109989502','http://dbpedia.org/class/yago/Singer110599806', 'wpath') #0.544
#Measuring YAGO concept similarity based on graph-based IC
sim.yago_similarity('http://dbpedia.org/class/yago/Dancer109989502','http://dbpedia.org/class/yago/Actor109765278', 'wpath_graph') #0.423
sim.yago_similarity('http://dbpedia.org/class/yago/Dancer109989502','http://dbpedia.org/class/yago/Singer110599806', 'wpath_graph') #0.328

Computing semantic similarity of DBpedia concepts.

from sematch.semantic.graph import DBpediaDataTransform, Taxonomy
from sematch.semantic.similarity import ConceptSimilarity
concept = ConceptSimilarity(Taxonomy(DBpediaDataTransform()),'models/dbpedia_type_ic.txt')
concept.name2concept('actor')
concept.similarity('http://dbpedia.org/ontology/Actor','http://dbpedia.org/ontology/Film', 'path')
concept.similarity('http://dbpedia.org/ontology/Actor','http://dbpedia.org/ontology/Film', 'wup')
concept.similarity('http://dbpedia.org/ontology/Actor','http://dbpedia.org/ontology/Film', 'li')
concept.similarity('http://dbpedia.org/ontology/Actor','http://dbpedia.org/ontology/Film', 'res')
concept.similarity('http://dbpedia.org/ontology/Actor','http://dbpedia.org/ontology/Film', 'lin')
concept.similarity('http://dbpedia.org/ontology/Actor','http://dbpedia.org/ontology/Film', 'jcn')
concept.similarity('http://dbpedia.org/ontology/Actor','http://dbpedia.org/ontology/Film', 'wpath')

Computing semantic similarity of DBpedia entities.

from sematch.semantic.similarity import EntitySimilarity
sim = EntitySimilarity()
sim.similarity('http://dbpedia.org/resource/Madrid','http://dbpedia.org/resource/Barcelona') #0.409923677282
sim.similarity('http://dbpedia.org/resource/Apple_Inc.','http://dbpedia.org/resource/Steve_Jobs')#0.0904545454545
sim.relatedness('http://dbpedia.org/resource/Madrid','http://dbpedia.org/resource/Barcelona')#0.457984139871
sim.relatedness('http://dbpedia.org/resource/Apple_Inc.','http://dbpedia.org/resource/Steve_Jobs')#0.465991132787

Evaluate semantic similarity metrics with word similarity datasets

from sematch.evaluation import WordSimEvaluation
from sematch.semantic.similarity import WordNetSimilarity
evaluation = WordSimEvaluation()
evaluation.dataset_names()
wns = WordNetSimilarity()
# define similarity metrics
wpath = lambda x, y: wns.word_similarity_wpath(x, y, 0.8)
# evaluate similarity metrics with SimLex dataset
evaluation.evaluate_metric('wpath', wpath, 'noun_simlex')
# performa Steiger's Z significance Test
evaluation.statistical_test('wpath', 'path', 'noun_simlex')
# define similarity metrics for Spanish words
wpath_es = lambda x, y: wns.monol_word_similarity(x, y, 'spa', 'path')
# define cross-lingual similarity metrics for English-Spanish
wpath_en_es = lambda x, y: wns.crossl_word_similarity(x, y, 'eng', 'spa', 'wpath')
# evaluate metrics in multilingual word similarity datasets
evaluation.evaluate_metric('wpath_es', wpath_es, 'rg65_spanish')
evaluation.evaluate_metric('wpath_en_es', wpath_en_es, 'rg65_EN-ES')

Evaluate semantic similarity metrics with category classification

Although the word similarity correlation measure is the standard way to evaluate the semantic similarity metrics, it relies on human judgements over word pairs which may not have same performance in real applications. Therefore, apart from word similarity evaluation, the Sematch evaluation framework also includes a simple aspect category classification. The task classifies noun concepts such as pasta, noodle, steak, tea into their ontological parent concept FOOD, DRINKS.

from sematch.evaluation import AspectEvaluation
from sematch.application import SimClassifier, SimSVMClassifier
from sematch.semantic.similarity import WordNetSimilarity

# create aspect classification evaluation
evaluation = AspectEvaluation()
# load the dataset
X, y = evaluation.load_dataset()
# define word similarity function
wns = WordNetSimilarity()
word_sim = lambda x, y: wns.word_similarity(x, y)
# Train and evaluate metrics with unsupervised classification model
simclassifier = SimClassifier.train(zip(X,y), word_sim)
evaluation.evaluate(X,y, simclassifier)

macro averge:  (0.65319812882333839, 0.7101245049198579, 0.66317566364913016, None)
micro average:  (0.79210167952791644, 0.79210167952791644, 0.79210167952791644, None)
weighted average:  (0.80842645056024054, 0.79210167952791644, 0.79639496616636352, None)
accuracy:  0.792101679528
             precision    recall  f1-score   support

    SERVICE       0.50      0.43      0.46       519
 RESTAURANT       0.81      0.66      0.73       228
       FOOD       0.95      0.87      0.91      2256
   LOCATION       0.26      0.67      0.37        54
   AMBIENCE       0.60      0.70      0.65       597
     DRINKS       0.81      0.93      0.87       752

avg / total       0.81      0.79      0.80      4406

Matching Entities with type using SPARQL queries

You can use Sematch to download a list of entities having a specific type using different languages. Sematch will generate SPARQL queries and execute them in DBpedia Sparql Endpoint.

from sematch.application import Matcher
matcher = Matcher()
# matching scientist entities from DBpedia
matcher.match_type('scientist')
matcher.match_type('científico', 'spa')
matcher.match_type('科学家', 'cmn')
matcher.match_entity_type('movies with Tom Cruise')

Example of automatically generated SPARQL query.

SELECT DISTINCT ?s, ?label, ?abstract WHERE {
    {  
    ?s <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/class/yago/NuclearPhysicist110364643> . }
 UNION {  
    ?s <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/class/yago/Econometrician110043491> . }
 UNION {  
    ?s <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/class/yago/Sociologist110620758> . }
 UNION {  
    ?s <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/class/yago/Archeologist109804806> . }
 UNION {  
    ?s <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/class/yago/Neurolinguist110354053> . } 
    ?s <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://www.w3.org/2002/07/owl#Thing> . 
    ?s <http://www.w3.org/2000/01/rdf-schema#label> ?label . 
    FILTER( lang(?label) = "en") . 
    ?s <http://dbpedia.org/ontology/abstract> ?abstract . 
    FILTER( lang(?abstract) = "en") .
} LIMIT 5000

Entity feature extraction with Similarity Graph

Apart from semantic matching of entities from DBpedia, you can also use Sematch to extract features of entities and apply semantic similarity analysis using graph-based ranking algorithms. Given a list of objects (concepts, words, entities), Sematch compute their pairwise semantic similarity and generate similarity graph where nodes denote objects and edges denote similarity scores. An example of using similarity graph for extracting important words from an entity description.

from sematch.semantic.graph import SimGraph
from sematch.semantic.similarity import WordNetSimilarity
from sematch.nlp import Extraction, word_process
from sematch.semantic.sparql import EntityFeatures
from collections import Counter
tom = EntityFeatures().features('http://dbpedia.org/resource/Tom_Cruise')
words = Extraction().extract_nouns(tom['abstract'])
words = word_process(words)
wns = WordNetSimilarity()
word_graph = SimGraph(words, wns.word_similarity)
word_scores = word_graph.page_rank()
words, scores =zip(*Counter(word_scores).most_common(10))
print words
(u'picture', u'action', u'number', u'film', u'post', u'sport', 
u'program', u'men', u'performance', u'motion')

Publications

Ganggao Zhu, and Carlos A. Iglesias. "Computing Semantic Similarity of Concepts in Knowledge Graphs." IEEE Transactions on Knowledge and Data Engineering 29.1 (2017): 72-85.

Oscar Araque, Ganggao Zhu, Manuel Garcia-Amado and Carlos A. Iglesias Mining the Opinionated Web: Classification and Detection of Aspect Contexts for Aspect Based Sentiment Analysis, ICDM sentire, 2016.

Ganggao Zhu, and Carlos Angel Iglesias. "Sematch: Semantic Entity Search from Knowledge Graph." SumPre-HSWI@ ESWC. 2015.


Support

You can post bug reports and feature requests in Github issues. Make sure to read our guidelines first. This project is still under active development approaching to its goals. The project is mainly maintained by Ganggao Zhu. You can contact him via gzhu [at] dit.upm.es


Why this name, Sematch and Logo?

The name of Sematch is composed based on Spanish "se" and English "match". It is also the abbreviation of semantic matching because semantic similarity metrics helps to determine semantic distance of concepts, words, entities, instead of exact matching.

The logo of Sematch is based on Chinese Yin and Yang which is written in I Ching. Somehow, it correlates to 0 and 1 in computer science.

Author: Gsi-upm
Source Code: https://github.com/gsi-upm/sematch 
License: View license

#python #jupyternotebook #graph 

Top 10 API Security Threats Every API Team Should Know

As more and more data is exposed via APIs either as API-first companies or for the explosion of single page apps/JAMStack, API security can no longer be an afterthought. The hard part about APIs is that it provides direct access to large amounts of data while bypassing browser precautions. Instead of worrying about SQL injection and XSS issues, you should be concerned about the bad actor who was able to paginate through all your customer records and their data.

Typical prevention mechanisms like Captchas and browser fingerprinting won’t work since APIs by design need to handle a very large number of API accesses even by a single customer. So where do you start? The first thing is to put yourself in the shoes of a hacker and then instrument your APIs to detect and block common attacks along with unknown unknowns for zero-day exploits. Some of these are on the OWASP Security API list, but not all.

Insecure pagination and resource limits

Most APIs provide access to resources that are lists of entities such as /users or /widgets. A client such as a browser would typically filter and paginate through this list to limit the number items returned to a client like so:

First Call: GET /items?skip=0&take=10 
Second Call: GET /items?skip=10&take=10

However, if that entity has any PII or other information, then a hacker could scrape that endpoint to get a dump of all entities in your database. This could be most dangerous if those entities accidently exposed PII or other sensitive information, but could also be dangerous in providing competitors or others with adoption and usage stats for your business or provide scammers with a way to get large email lists. See how Venmo data was scraped

A naive protection mechanism would be to check the take count and throw an error if greater than 100 or 1000. The problem with this is two-fold:

  1. For data APIs, legitimate customers may need to fetch and sync a large number of records such as via cron jobs. Artificially small pagination limits can force your API to be very chatty decreasing overall throughput. Max limits are to ensure memory and scalability requirements are met (and prevent certain DDoS attacks), not to guarantee security.
  2. This offers zero protection to a hacker that writes a simple script that sleeps a random delay between repeated accesses.
skip = 0
while True:    response = requests.post('https://api.acmeinc.com/widgets?take=10&skip=' + skip),                      headers={'Authorization': 'Bearer' + ' ' + sys.argv[1]})    print("Fetched 10 items")    sleep(randint(100,1000))    skip += 10

How to secure against pagination attacks

To secure against pagination attacks, you should track how many items of a single resource are accessed within a certain time period for each user or API key rather than just at the request level. By tracking API resource access at the user level, you can block a user or API key once they hit a threshold such as “touched 1,000,000 items in a one hour period”. This is dependent on your API use case and can even be dependent on their subscription with you. Like a Captcha, this can slow down the speed that a hacker can exploit your API, like a Captcha if they have to create a new user account manually to create a new API key.

Insecure API key generation

Most APIs are protected by some sort of API key or JWT (JSON Web Token). This provides a natural way to track and protect your API as API security tools can detect abnormal API behavior and block access to an API key automatically. However, hackers will want to outsmart these mechanisms by generating and using a large pool of API keys from a large number of users just like a web hacker would use a large pool of IP addresses to circumvent DDoS protection.

How to secure against API key pools

The easiest way to secure against these types of attacks is by requiring a human to sign up for your service and generate API keys. Bot traffic can be prevented with things like Captcha and 2-Factor Authentication. Unless there is a legitimate business case, new users who sign up for your service should not have the ability to generate API keys programmatically. Instead, only trusted customers should have the ability to generate API keys programmatically. Go one step further and ensure any anomaly detection for abnormal behavior is done at the user and account level, not just for each API key.

Accidental key exposure

APIs are used in a way that increases the probability credentials are leaked:

  1. APIs are expected to be accessed over indefinite time periods, which increases the probability that a hacker obtains a valid API key that’s not expired. You save that API key in a server environment variable and forget about it. This is a drastic contrast to a user logging into an interactive website where the session expires after a short duration.
  2. The consumer of an API has direct access to the credentials such as when debugging via Postman or CURL. It only takes a single developer to accidently copy/pastes the CURL command containing the API key into a public forum like in GitHub Issues or Stack Overflow.
  3. API keys are usually bearer tokens without requiring any other identifying information. APIs cannot leverage things like one-time use tokens or 2-factor authentication.

If a key is exposed due to user error, one may think you as the API provider has any blame. However, security is all about reducing surface area and risk. Treat your customer data as if it’s your own and help them by adding guards that prevent accidental key exposure.

How to prevent accidental key exposure

The easiest way to prevent key exposure is by leveraging two tokens rather than one. A refresh token is stored as an environment variable and can only be used to generate short lived access tokens. Unlike the refresh token, these short lived tokens can access the resources, but are time limited such as in hours or days.

The customer will store the refresh token with other API keys. Then your SDK will generate access tokens on SDK init or when the last access token expires. If a CURL command gets pasted into a GitHub issue, then a hacker would need to use it within hours reducing the attack vector (unless it was the actual refresh token which is low probability)

Exposure to DDoS attacks

APIs open up entirely new business models where customers can access your API platform programmatically. However, this can make DDoS protection tricky. Most DDoS protection is designed to absorb and reject a large number of requests from bad actors during DDoS attacks but still need to let the good ones through. This requires fingerprinting the HTTP requests to check against what looks like bot traffic. This is much harder for API products as all traffic looks like bot traffic and is not coming from a browser where things like cookies are present.

Stopping DDoS attacks

The magical part about APIs is almost every access requires an API Key. If a request doesn’t have an API key, you can automatically reject it which is lightweight on your servers (Ensure authentication is short circuited very early before later middleware like request JSON parsing). So then how do you handle authenticated requests? The easiest is to leverage rate limit counters for each API key such as to handle X requests per minute and reject those above the threshold with a 429 HTTP response. There are a variety of algorithms to do this such as leaky bucket and fixed window counters.

Incorrect server security

APIs are no different than web servers when it comes to good server hygiene. Data can be leaked due to misconfigured SSL certificate or allowing non-HTTPS traffic. For modern applications, there is very little reason to accept non-HTTPS requests, but a customer could mistakenly issue a non HTTP request from their application or CURL exposing the API key. APIs do not have the protection of a browser so things like HSTS or redirect to HTTPS offer no protection.

How to ensure proper SSL

Test your SSL implementation over at Qualys SSL Test or similar tool. You should also block all non-HTTP requests which can be done within your load balancer. You should also remove any HTTP headers scrub any error messages that leak implementation details. If your API is used only by your own apps or can only be accessed server-side, then review Authoritative guide to Cross-Origin Resource Sharing for REST APIs

Incorrect caching headers

APIs provide access to dynamic data that’s scoped to each API key. Any caching implementation should have the ability to scope to an API key to prevent cross-pollution. Even if you don’t cache anything in your infrastructure, you could expose your customers to security holes. If a customer with a proxy server was using multiple API keys such as one for development and one for production, then they could see cross-pollinated data.

#api management #api security #api best practices #api providers #security analytics #api management policies #api access tokens #api access #api security risks #api access keys

Autumn  Blick

Autumn Blick

1601381326

Public ASX100 APIs: The Essential List

We’ve conducted some initial research into the public APIs of the ASX100 because we regularly have conversations about what others are doing with their APIs and what best practices look like. Being able to point to good local examples and explain what is happening in Australia is a key part of this conversation.

Method

The method used for this initial research was to obtain a list of the ASX100 (as of 18 September 2020). Then work through each company looking at the following:

  1. Whether the company had a public API: this was found by googling “[company name] API” and “[company name] API developer” and “[company name] developer portal”. Sometimes the company’s website was navigated or searched.
  2. Some data points about the API were noted, such as the URL of the portal/documentation and the method they used to publish the API (portal, documentation, web page).
  3. Observations were recorded that piqued the interest of the researchers (you will find these below).
  4. Other notes were made to support future research.
  5. You will find a summary of the data in the infographic below.

Data

With regards to how the APIs are shared:

#api #api-development #api-analytics #apis #api-integration #api-testing #api-security #api-gateway

An API-First Approach For Designing Restful APIs | Hacker Noon

I’ve been working with Restful APIs for some time now and one thing that I love to do is to talk about APIs.

So, today I will show you how to build an API using the API-First approach and Design First with OpenAPI Specification.

First thing first, if you don’t know what’s an API-First approach means, it would be nice you stop reading this and check the blog post that I wrote to the Farfetchs blog where I explain everything that you need to know to start an API using API-First.

Preparing the ground

Before you get your hands dirty, let’s prepare the ground and understand the use case that will be developed.

Tools

If you desire to reproduce the examples that will be shown here, you will need some of those items below.

  • NodeJS
  • OpenAPI Specification
  • Text Editor (I’ll use VSCode)
  • Command Line

Use Case

To keep easy to understand, let’s use the Todo List App, it is a very common concept beyond the software development community.

#api #rest-api #openai #api-first-development #api-design #apis #restful-apis #restful-api