3,316 reputation
620
bio website ripple.com
location Oakland, CA
age 44
visits member for 2 years, 11 months
seen 2 days ago

I am Chief Cryptographer at Ripple Labs and one of the architects of the Ripple payment system.


Jul
2
awarded  Curious
Jun
6
awarded  Nice Answer
Feb
20
awarded  Nice Question
Feb
4
comment Signing the hash of a key with the same key
Would people really use a signature scheme were signing a piece of public information could compromise your signing key? Wouldn't that be an obvious catastrophic deficiency?
Nov
22
awarded  Enlightened
Nov
22
awarded  Nice Answer
Sep
3
comment Elliptic Curve Cryptography Encryption Results
RSA does not involve any randomness, but it is trivially breakable (if used in the context involved here). Say I send you a message in plaintext, "Should we attack? Respond 'yes' or 'no' encrypting with RSA." This is trivially breakable, you can just trial encrypt both the 'yes' and the 'no'. This is one of the reasons RSA is not used alone. A public key algorithm that operates on short plaintext (which is what we're talking about here) must involve some randomness or it's trivially breakable by trial encryption.
Sep
1
answered Elliptic Curve Cryptography Encryption Results
Aug
28
comment Should I delete cryptographic data from memory?
What are you trying to prevent exactly? Presumably an "attacker" who had access to the machine's memory would thereby be entitled to the data the machine had processed. And if your model is that an attacker may have control over the machine while it's processing the data, erasing it later won't help. Are you trying to protect against sensitive data in swap or core dumps?
Aug
13
awarded  Yearling
Jul
31
awarded  Nice Answer
Jul
4
awarded  Tag Editor
Jul
4
revised length-extension wiki description
The MAC/hash does change, it just changes in a way that allows the attacker to maintain its validity.
Jul
4
suggested suggested edit on length-extension tag wiki
Jul
4
awarded  Custodian
Jul
4
reviewed Approve suggested edit on length-extension tag wiki
Jul
4
reviewed Approve suggested edit on length-extension tag wiki excerpt
Jul
4
comment Cryptographic Challenge: How to Say Something Confidentially to Snowden?
You must have some way, in principle, to identify Snowden. If you have such a way, we must know what it is. If you do not, then it is provably impossible -- anything that identifies the Snowden you have in mind could also identify someone else.
Jun
21
comment Is there a hash function which has no collisions?
@improv32: Just use any encryption scheme you like with a key much shorter than the data. (You can easily remove this requirement if needed.) To later prove you had the data earlier, release the key you encrypted it with.
May
12
awarded  Good Answer