hash_sha256

This page explains how to use the hash_sha256 function in APL.

Introduction

The hash_sha256 function returns the SHA-256 hash of a scalar value as a 64-character hexadecimal string. Use it for security-sensitive hashing, compliance requirements, data integrity checks, or any scenario where cryptographic strength is needed.

SHA-256 produces a 256-bit digest and is the current industry standard for secure hashing. Unlike MD5 and SHA-1, SHA-256 isn't practically vulnerable to collision attacks, making it appropriate for use in security workflows such as verifying log integrity, fingerprinting malware indicators, or hashing credentials. For even longer digests, use hash_sha512.

Usage

Syntax

APL

hash_sha256(source)

Parameters

Name	Type	Required	Description
source	scalar	Yes	The value to hash. APL converts it to a string before hashing.

Returns

The SHA-256 hash of source as a 64-character lowercase hexadecimal string.

Use case examples

Anonymize user IDs with a cryptographically strong hash before publishing usage summaries.

Query

APLRun in Playground

['sample-http-logs']
| extend hashed_id = hash_sha256(id)
| summarize request_count = count() by hashed_id
| top 5 by request_count

Output

hashed_id	request_count
bb4770ff4ac5b7d2be41a088cb27d8bcaad53b574b6f27941e8e48e9e10fc25a	128
2c624232cdd221771294dfbb310acbc8c12eb62dd7a3b4bfc41de8dd73d7a7c	97
19581e27de7ced00ff1ce50b2047e7a567c76b1cbaebabe5ef03f7c3017bb5b7	85
4b227777d4dd1fc61c6f884f48641d02b4d121d3fd328cb5bda0e1b1b68a2a3e	74
ef2d127de37b942baad06145e54b0c619a1f22327b2ebbcfbec78f5564afe39d	69

The query replaces user IDs with SHA-256 hashes before aggregating, producing a privacy-safe summary of the most active users.

Fingerprint trace IDs with SHA-256 for use in external security or compliance systems.

Query

APLRun in Playground

['otel-demo-traces']
| extend hashed_trace = hash_sha256(trace_id)
| project _time, ['service.name'], hashed_trace, duration
| take 10

Output

_time	service.name	hashed_trace	duration
2024-01-15 10:23:01	frontend	bb4770ff4ac5b7d2be41a088cb27d8bcaad53b574b6f27941e8e48e9e10fc25a	320ms
2024-01-15 10:23:02	checkout	2c624232cdd221771294dfbb310acbc8c12eb62dd7a3b4bfc41de8dd73d7a7c	875ms
2024-01-15 10:23:03	cart	19581e27de7ced00ff1ce50b2047e7a567c76b1cbaebabe5ef03f7c3017bb5b7	140ms

The query outputs hashed trace IDs that can be shared with external audit or compliance tools without exposing internal identifiers.

hash_sha512: Returns a 128-character SHA-512 hex digest. Use hash_sha512 when your security policy requires a longer digest than SHA-256.
hash_sha1: Returns a 40-character SHA-1 hex digest. SHA-1 is deprecated for security use; prefer hash_sha256.
hash_md5: Returns a 32-character MD5 hex digest. MD5 isn't cryptographically safe; use hash_sha256 for security contexts.
hash: Returns a signed 64-bit integer hash. Use hash when you need a compact numeric key rather than a hex string.