It's pretty easy to eyeball your ciphertext and think it's sufficiently garbage-looking, but it's difficult to predict what an attacker can do with access to your running system. Seemingly innocuous flaws can lead to complete plaintext recovery or the ability to forge arbitrary ciphertext. (Here's a fun way to get a taste: http://www.matasano.com/articles/crypto-challenges/)
@cperciva is right that cryptographic security is something that needs to be proven. Since I'm not smart enough to do that, I avoid designing my own crypto systems, and I recommend clients do the same. Lots of risk, little or no reward.
It's pretty easy to eyeball your ciphertext and think it's sufficiently garbage-looking, but it's difficult to predict what an attacker can do with access to your running system. Seemingly innocuous flaws can lead to complete plaintext recovery or the ability to forge arbitrary ciphertext. (Here's a fun way to get a taste: http://www.matasano.com/articles/crypto-challenges/)
@cperciva is right that cryptographic security is something that needs to be proven. Since I'm not smart enough to do that, I avoid designing my own crypto systems, and I recommend clients do the same. Lots of risk, little or no reward.