I intend to update this site over Christmas 2020. Please contact me with any updates, if I have made any mistakes. 

Comparison	Allo	iMessage	Messenger	Riot	Signal	Skype	Telegram	Threema	Viber	Whatsapp	Wickr	Wire
TL;DR: Does the app secure my messages and attachments?	No	No	No	No	Yes	No	No	Yes	No	No	No	Yes
Company jurisdiction	USA	USA	USA	UK	USA	USA	USA / UK / Belize	Switzerland	Luxembourg / Japan	USA	USA	Switzerland
Infrastructure jurisdiction	USA, Belgium, Finland, Ireland,the Netherlands, Chile, Taiwan,and Singapore	USA (Ireland and Denmark planned); iMessage runs on AWS and Google Cloud	USA, Sweden (Ireland planned)	UK (and potentially all jurisdictions, given it's a decentralised messaging platform)	USA	USA, the Netherlands, Australia, Brazil, China, Ireland, Hong Kong, and Japan	UK, Singapore, USA, and Finland	Switzerland	USA	USA (unsure of other locations)	USA (unsure of other locations)	Germany / Ireland
Implicated in giving customers' data to intelligence agencies?	Yes	Yes	Yes	No	No	Yes	No	No	No	Yes	No	No
Surveillance capability built into the app?	No	No	No	No	No	Yes	No	No	No	No	No	No
Does the company provide a transparency report?	Yes	Yes	Yes	No	Yes	Yes	No	Yes	No	Yes	Yes	Yes
Company's general stance on customers' privacy	Poor	Poor	Poor	Good	Good	Poor	Poor	Good	Poor	Poor	Good	Good
Funding	Google	Apple	Facebook	New Vector Limited	Freedom of the Press Foundation, the Knight Foundation, the Shuttleworth Foundation, and the Open Technology Fund, Signal Foundation (Brian Acton)	Microsoft	Pavel Durov	User pays	Rakuten, friends and family of Talmon Marco (it's very unclear)	Facebook	Gilman Louie, Juniper Networks, the Knight Foundation, Breyer Capital, CME Group, and Wargaming	Janus Friis, Iconical, Zeta Holdings Luxembourg
Company collects customers' data?	Yes	Yes	Yes	No	No	Yes	Yes	No	Yes	Yes	No	No
App collects customers' data?	Yes	Yes	Yes	Minimal	Minimal	Yes	Yes	No	Yes	Yes	No	Minimal
Is encryption turned on by default?	No	Yes	No	No	Yes	Yes	No	Yes	Yes (if device supports it)	Yes (if device supports it)	Yes	Yes
Cryptographic primitives		RSA-1280 (encryption), ECDSA 256 (signing) / AES 128 / SHA-1	Curve25519 / AES-256 / HMAC-SHA256	Curve25519 / AES-256 / HMAC-SHA256	Curve25519 / AES-256 / HMAC-SHA256	RSA-1536 & 2048 / AES 256 / SHA-1	RSA 2048 / AES 256 / SHA-256	Curve25519 256 / XSalsa20 256 / Poly1305-AES 128	Curve25519 256 / Salsa20 128 / HMAC-SHA256	Curve25519 / AES-256 / HMAC-SHA256	ECDH512 / AES-256 / HMAC-SHA256	Curve25519 / ChaCha20 / HMAC-SHA256
Are the app and server completely open source?	No	No	No	Yes	Yes	No	No (clients and API only)	No	No	No	No	Yes
Can you sign up to the app anonymously?	No	No	No	Yes	No	No	No	Yes	No	No	Yes	No
Can you add a contact without needing to trust a directory server?	No	No	No	No	No	No	No	Yes	Yes	No	No	No
Can you manually verify contacts' fingerprints?	No	No	Yes	Yes	Yes	No	No (session only, does not provide users' fingerprint information)	Yes	Yes	Yes	Yes	Yes
Directory service could be modified to enable a MITM attack?	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Do you get notified if a contact's fingerprint changes?	No	No		Yes	Yes	No	No (session only, does not provide users' fingerprint information)	Yes	Yes	No (setting turned off by default)	No	If contact was previously verified
Is personal information (mobile number, contact list, etc.) hashed?	No	No	No		Mostly	No	No	Yes	No	No	Yes	Mostly
Does the app generate & keep a private key on the device itself?		Yes	Yes	Yes	Yes		Yes	Yes	Yes	Yes	Yes	Yes
Can messages be read by the company?	Yes	No	Yes	No	No	Yes	Yes	No	No	No	No	No
Does the app enforce perfect forward secrecy?		No	Yes	Yes	Yes		No (session keys do change after being used 100 times)	No	Yes	Yes	Yes	Yes
Does the app encrypt metadata?		No	No		Yes		No	Yes		No	Yes	Mostly
Does the app use TLS/Noise to encrypt network traffic?	Yes	Yes	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes
Does the app use certificate pinning?		Yes (>=iOS 9.3)			Yes			Yes				Yes
Does the app encrypt data on the device? (iOS and Android only)		Yes (if passphrase enabled)			Yes (if passphrase enabled)			iOS: Yes (if passphrase enabled); Android: Yes (if master key set in the app)			iOS: Yes (if passphrase enabled); Android: Yes (unsure of function)	Yes
Does the app allow a secondary factor of authentication?	No	No	No	No	No	No	Yes	Yes	No	Yes	Yes (password for account used)	Yes
Are messages encrypted when backed up to the cloud?		No			N/A, Signal is excluded from iCloud/iTunes & Android backups			Yes		iOS: Yes Android: No		N/A, Wire is excluded from iCloud/iTunes & Android backups
Does the company log timestamps/IP addresses?	Yes	Yes	Yes		No	Yes	Yes	No	Yes	Yes	No	Some
Have there been a recent code audit and an independent security analysis?	No	No	No	No	Yes (October, 2014)	No	Yes (November, 2015)	Yes (November, 2015)	No	No	Yes (August, 2014)	Yes (March, 2018)
Is the design well documented?	No	Somewhat	Somewhat	Somewhat	Somewhat	No	Somewhat	Somewhat	Somewhat	Somewhat	Somewhat	Somewhat
Does the app have self-destructing messages?	Yes	No	Yes	No	Yes	No	Yes	No	No	No	Yes	Yes

Red = Something of major concern.

Yellow = Something of concern.

Green = Nothing of concern.

Blank = I couldn’t find any information about it.